{"id":122464,"date":"2026-11-04T23:41:09","date_gmt":"2026-11-04T15:41:09","guid":{"rendered":"https:\/\/www.wsisp.com\/helps\/122464.html"},"modified":"2026-11-04T23:41:09","modified_gmt":"2026-11-04T15:41:09","slug":"%e4%b8%80%e5%a4%a9%e5%90%83%e9%80%8f-string-%e4%b8%8e-stringbuilder%ef%bc%9a%e4%bb%8e-api-%e6%96%87%e6%a1%a3%e5%88%b0%e5%ad%97%e7%ac%a6%e4%b8%b2%e5%a4%a7%e6%95%b0%e7%9b%b8%e5%8a%a0","status":"publish","type":"post","link":"https:\/\/www.wsisp.com\/helps\/122464.html","title":{"rendered":"\u4e00\u5929\u5403\u900f String \u4e0e StringBuilder\uff1a\u4ece API \u6587\u6863\u5230\u5b57\u7b26\u4e32\u5927\u6570\u76f8\u52a0"},"content":{"rendered":"

\/* MD \/ \u5bcc\u6587\u672c\u4e2d\u7684 .toc\uff08\u542b\u535a\u5ba2\u56ed\u642c\u5bb6\u7b49\u5d4c\u5957\u7ed3\u6784\uff09\uff1b.toc-box \u5728\u4fa7\u680f\uff0c\u4e0d\u53d7\u5f71\u54cd *\/
\n #content_views .toc,
\n \/* \u7f16\u8f91\u5668\u5e38\u5728\u76ee\u5f55\u524d\u540e\u63d2\u5165\u7a7a p\uff08:empty \u4ecd\u5360 20px\uff09\uff0c\u4e00\u5e76\u53bb\u6389\u907f\u514d\u9876\u7a7a\u9699 *\/
\n #content_views.markdown_views > p:empty:has(+ .toc),
\n #content_views.markdown_views > .toc + p:empty,
\n \/* \u5bcc\u6587\u672c\u65e7\u7248\u76ee\u5f55\u6807\u8bb0 *\/
\n #content_views.htmledit_views #main-toc,
\n #content_views.htmledit_views #hr-toc,
\n #content_views.htmledit_views p[id*=\\”-toc\\”] {
\n display: none !important;
\n }
\n \/* \u76ee\u5f55\u53bb\u6389\u540e\uff0c\u7d27\u8ddf\u7684\u9996\u4e2a\u6807\u9898\u4e0d\u518d\u591a\u51fa\u4e00\u5757\u4e0a\u8fb9\u8ddd *\/
\n #content_views.markdown_views > .toc + h1,
\n #content_views.markdown_views > .toc + h2,
\n #content_views.markdown_views > .toc + h3,
\n #content_views.markdown_views > .toc + h4,
\n #content_views.markdown_views > .toc + p:empty + h1,
\n #content_views.markdown_views > .toc + p:empty + h2,
\n #content_views.markdown_views > .toc + p:empty + h3,
\n #content_views.markdown_views > .toc + p:empty + h4 {
\n margin-top: 0 !important;
\n }<\/p>\n

Java\u5b66\u4e60\u8bb0\u5f55<\/h2>\n

\u65e5\u671f： 10.16<\/p>\n

📖\u4eca\u65e5\u77e5\u8bc6\u70b9 \u2014\u2014API\u548cAPI\u5e2e\u52a9\u6587\u6863<\/h3>\n

API：\u5e94\u7528\u7a0b\u5e8f\u7f16\u8f91\u63a5\u53e3<\/h4>\n

\u7b80\u5355\u7406\u89e3：\u5c31\u662fJDK\u63d0\u4f9b\u7684\u5404\u79cd\u529f\u80fd\u7684Java\u7c7b\u3002\u6211\u4eec\u4e0d\u9700\u8981\u81ea\u5df1\u7f16\u5199，\u76f4\u63a5\u4f7f\u7528\u5373\u53ef\u3002\u8fd9\u4e9b\u7c7b\u5c06\u5e95\u5c42\u7684\u5b9e\u73b0\u5c01\u88c5\u4e86\u8d77\u6765，\u6211\u4eec\u4e0d\u9700\u8981\u5173\u5fc3\u8fd9\u4e9b\u7c7b\u662f\u5982\u4f55\u5b9e\u73b0\u7684，\u53ea\u8981\u5b66\u4f1a\u5982\u4f55\u4f7f\u7528\u3002<\/p>\n

API\u5e2e\u52a9\u6587\u6863：\u5e2e\u52a9\u5f00\u53d1\u4eba\u5458\u66f4\u597d\u5730\u4f7f\u7528API\u548c\u67e5\u8be2API\u7684\u4e00\u4e2a\u5de5\u5177<\/h4>\n

\u5982\u4f55\u4f7f\u7528\u5e2e\u52a9\u6587\u6863 (API\u6587\u6863)<\/h4>\n

\u64cd\u4f5c\u6b65\u9aa4：
\n1\u3001\u6253\u5f00API\u5e2e\u52a9\u6587\u6863<\/p>\n

2\u3001\u70b9\u51fb\u663e\u793a，\u5e76\u627e\u5230\u7d22\u5f15\u4e0b\u9762\u7684\u8f93\u5165\u6846<\/p>\n

3\u3001\u5728\u8f93\u5165\u6846\u4e2d\u8f93\u5165\u7c7b\u540d\u5e76\u70b9\u51fb\u663e\u793a<\/p>\n

4\u3001\u67e5\u770b\u7c7b\u6240\u5728\u7684\u5305<\/p>\n

5\u3001\u67e5\u770b\u7c7b\u7684\u63cf\u8ff0<\/p>\n

6\u3001\u67e5\u770b\u6784\u9020\u65b9\u6cd5<\/p>\n

7\u3001\u67e5\u770b\u6210\u5458\u65b9\u6cd5 (\u91cd\u70b9\u5173\u6ce8\u5e26\u53c2\u6570\u7684\u65b9\u6cd5)<\/p>\n

💻\u7ec3\u4e60\u4ee3\u7801<\/h3>\n

package<\/span> com.<\/span>itheima.<\/span>apidemo1<\/span>;<\/span>
\n\/\/\u5bfc\u5305：\u5b9a\u4f4dRandom\u7684\u4f4d\u7f6e<\/span>
\n\/\/\u6269\u5c55：\u5728\u4ec0\u4e48\u60c5\u51b5\u4e0b\u4e0d\u9700\u8981\u5bfc\u5305<\/span>
\n\/\/ 1\u3001\u4f7f\u7528\u5f53\u524d\u5305\u4e0b\u7684\u7c7b<\/span>
\n\/\/ 2\u3001\u4f7f\u7528java.lang\u5305\u4e0b\u7684\u7c7b<\/span>
\n\/\/ \u5176\u4ed6\u6240\u6709\u60c5\u51b5\u4e0b\u90fd\u9700\u8981\u5bfc\u5305<\/span>
\nimport<\/span> java.<\/span>util.<\/span><\/span>Random<\/span><\/span>;<\/span><\/p>\n

public<\/span> class<\/span> Test<\/span> {<\/span>
\n public<\/span> static<\/span> void<\/span> main<\/span>(<\/span>String<\/span>[<\/span>]<\/span> args)<\/span> {<\/span>
\n \/\/\u9700\u6c42：\u67e5\u8be2API\u5e2e\u52a9\u6587\u6863，\u4f7f\u7528Random\u7c7b\u4e2d\u83b7\u53d6\u968f\u673a\u5c0f\u6570\u7684\u65b9\u6cd5<\/span>
\n \/\/1\u3001\u521b\u5efaRandom\u7c7b\u5bf9\u8c61<\/span>
\n Random<\/span> r =<\/span> new<\/span> Random<\/span>(<\/span>)<\/span>;<\/span>
\n \/\/2\u3001\u4f7f\u7528\u5bf9\u8c61\u8c03\u7528\u65b9\u6cd5<\/span>
\n \/\/[0.0,1.0)<\/span>
\n double<\/span> d1 =<\/span> r.<\/span>nextDouble<\/span>(<\/span>)<\/span>;<\/span>
\n System<\/span>.<\/span>out.<\/span>println<\/span>(<\/span>d1)<\/span>;<\/span>
\n System<\/span>.<\/span>out.<\/span>println<\/span>(<\/span>"================"<\/span>)<\/span>;<\/span>
\n for<\/span> (<\/span>int<\/span> i =<\/span> 0<\/span>;<\/span> i <<\/span> 10<\/span>;<\/span> i++<\/span>)<\/span>{<\/span>
\n double<\/span> d2 =<\/span> r.<\/span>nextDouble<\/span>(<\/span>1.2<\/span>,<\/span>3.4<\/span> )<\/span>;<\/span>
\n System<\/span>.<\/span>out.<\/span>println<\/span>(<\/span>d2)<\/span>;<\/span>
\n }<\/span>
\n }<\/span>
\n}<\/span><\/p>\n

📖\u4eca\u65e5\u77e5\u8bc6\u70b9 \u2014\u2014\u5b57\u7b26\u4e32String<\/h3>\n

1\u3001String\u662fJava\u5b9a\u4e49\u597d\u7684\u4e00\u4e2a\u7c7b\u3002\u5b9a\u4e49\u5728 java.lang \u5305\u4e2d，\u4f7f\u7528\u7684\u65f6\u5019\u4e0d\u9700\u8981\u5bfc\u5305\u3002<\/p>\n

2\u3001Java \u7a0b\u5e8f\u4e2d\u7684\u6240\u6709\u5b57\u7b26\u4e32\u6587\u5b57（\u4f8b\u5982 \u201cabc\u201d ）\u90fd\u662f\u6b64\u7c7b\u7684\u5bf9\u8c61<\/p>\n

3\u3001\u5b57\u7b26\u4e32\u4e0d\u53ef\u53d8，\u5b83\u4eec\u7684\u503c\u5728\u521b\u5efa\u540e\u4e0d\u80fd\u88ab\u66f4\u6539<\/p>\n

💻\u7ec3\u4e60\u4ee3\u7801<\/h3>\n

package<\/span> com.<\/span>itheima.<\/span>apidemo2<\/span>;<\/span><\/p>\n

public<\/span> class<\/span> Test<\/span> {<\/span>
\n public<\/span> static<\/span> void<\/span> main<\/span>(<\/span>String<\/span>[<\/span>]<\/span> args)<\/span> {<\/span>
\n \/*
\n \u7b2c\u4e00\u79cd：\u76f4\u63a5\u8d4b\u503c
\n \u7b2c\u4e8c\u79cd：new\u5173\u952e\u5b57
\n public String() \u7a7a\u767d\u5b57\u7b26\u4e32，\u4e0d\u542b\u4efb\u4f55\u5185\u5bb9
\n public String(String original) \u6839\u636e\u4f20\u5165\u7684\u5b57\u7b26\u4e32，\u521b\u5efa\u65b0\u7684\u5b57\u7b26\u4e32\u5bf9\u8c61
\n public String(char[] chs) \u6839\u636e\u5b57\u7b26\u6570\u7ec4，\u521b\u5efa\u5b57\u7b26\u4e32\u5bf9\u8c61
\n public String(byte[] chs) \u6839\u636e\u5b57\u8282\u6570\u7ec4，\u521b\u5efa\u5b57\u7b26\u4e32\u5bf9\u8c61
\n *\/<\/span>
\n \/\/ 1. \u76f4\u63a5\u8d4b\u503c<\/span>
\n \/\/ \u6700\u7b80\u5355 \u6700\u5e38\u7528<\/span>
\n String<\/span> s =<\/span> "abc"<\/span>;<\/span>
\n System<\/span>.<\/span>out.<\/span>println<\/span>(<\/span>s)<\/span>;<\/span>
\n \/\/ 2.new + \u6784\u9020\u65b9\u6cd5\u7684\u65b9\u5f0f\u521b\u5efa\u5b57\u7b26\u4e32\u5bf9\u8c61<\/span>
\n \/\/ new + \u7a7a\u53c2\u6784\u9020<\/span>
\n String<\/span> s1 =<\/span> new<\/span> String<\/span>(<\/span>)<\/span>;<\/span>
\n System<\/span>.<\/span>out.<\/span>println<\/span>(<\/span>"=="<\/span>+<\/span> s1 +<\/span> "@@"<\/span>)<\/span>;<\/span>
\n \/\/3. new + \u5e26\u53c2\u6784\u9020<\/span>
\n String<\/span> s2 =<\/span> new<\/span> String<\/span>(<\/span>"abc"<\/span>)<\/span>;<\/span>
\n System<\/span>.<\/span>out.<\/span>println<\/span>(<\/span>s2)<\/span>;<\/span>
\n \/\/4. new + \u6709\u53c2\u6784\u9020（\u5b57\u7b26\u6570\u7ec4）<\/span>
\n char<\/span>[<\/span>]<\/span> ch =<\/span> {<\/span>'a'<\/span>,<\/span> 'b'<\/span>,<\/span> 'c'<\/span>}<\/span>;<\/span>
\n String<\/span> s3 =<\/span> new<\/span> String<\/span>(<\/span>ch)<\/span>;<\/span>
\n System<\/span>.<\/span>out.<\/span>println<\/span>(<\/span>s3)<\/span>;<\/span>
\n \/\/5.new + \u6709\u53c2\u6784\u9020（\u5b57\u8282\u6570\u7ec4）<\/span>
\n \/\/ASCII\u7801\u8868<\/span>
\n byte<\/span>[<\/span>]<\/span> by =<\/span> {<\/span>97<\/span>,<\/span> 98<\/span>,<\/span> 99<\/span>}<\/span>;<\/span>\/\/\u4e0d\u8981\u8d85\u8fc7127<\/span>
\n String<\/span> s4 =<\/span> new<\/span> String<\/span>(<\/span>by)<\/span>;<\/span>
\n System<\/span>.<\/span>out.<\/span>println<\/span>(<\/span>s4)<\/span>;<\/span>\/\/a b c<\/span>
\n }<\/span>
\n}<\/span><\/p>\n

📖\u4eca\u65e5\u77e5\u8bc6\u70b9 \u2014\u2014\u76f4\u63a5\u8d4b\u503c\u548cnew\u7684\u533a\u522b<\/h3>\n

\u83b7\u53d6\u5b57\u7b26\u4e32\u5bf9\u8c61\u7684\u4e24\u79cd\u65b9\u5f0f：<\/h4>\n

1\u3001\u76f4\u63a5\u8d4b\u503c：\u4ee3\u7801\u7b80\u5355 + \u4e32\u6c60\u590d\u7528<\/p>\n

2\u3001new：\u6bcf\u6b21\u90fd\u4f1a\u521b\u5efa\u4e00\u4e2a\u65b0\u7684\u5b57\u7b26\u4e32\u5bf9\u8c61
\n\"\u8bf7\u6dfb\u52a0\u56fe\u7247\u63cf\u8ff0\"
\n\"\u8bf7\u6dfb\u52a0\u56fe\u7247\u63cf\u8ff0\"<\/p>\n

📖\u4eca\u65e5\u77e5\u8bc6\u70b9 \u2014\u2014\u5b57\u7b26\u4e32\u7684\u6bd4\u8f83<\/h3>\n

\u5b57\u7b26\u4e32\u6bd4\u8f83<\/h4>\n

1\u3001boolean equals\u65b9\u6cd5(\u8981\u6bd4\u8f83\u7684\u5b57\u7b26\u4e32)：\u5b8c\u5168\u4e00\u6837\u7ed3\u679c\u624d\u662ftrue，\u5426\u5219\u4e3afalse<\/p>\n

2\u3001boolean equalsIgnoreCase(\u8981\u6bd4\u8f83\u7684\u5b57\u7b26\u4e32)：\u5ffd\u7565\u5927\u5c0f\u5199\u7684\u6bd4\u8f83<\/p>\n

💻\u7ec3\u4e60\u4ee3\u7801<\/h3>\n

package<\/span> com.<\/span>itheima.<\/span>apidemo3<\/span>;<\/span><\/p>\n

import<\/span> java.<\/span>util.<\/span><\/span>Scanner<\/span><\/span>;<\/span><\/p>\n

public<\/span> class<\/span> Test<\/span> {<\/span>
\n public<\/span> static<\/span> void<\/span> main<\/span>(<\/span>String<\/span>[<\/span>]<\/span> args)<\/span> {<\/span>
\n \/*
\n \u5b57\u7b26\u4e32\u6bd4\u8f83
\n 1.boolean equals\u65b9\u6cd5(\u8981\u6bd4\u8f83\u7684\u5b57\u7b26\u4e32)：\u5b8c\u5168\u4e00\u6837\u7ed3\u679c\u624d\u662ftrue，\u5426\u5219\u4e3afalse
\n 2.boolean equalsIgnoreCase(\u8981\u6bd4\u8f83\u7684\u5b57\u7b26\u4e32)：\u5ffd\u7565\u5927\u5c0f\u5199\u7684\u6bd4\u8f83<\/p>\n

\u9700\u6c42： \u5df2\u77e5\u6b63\u786e\u7684\u7528\u6237\u540d\u548c\u5bc6\u7801，\u8bf7\u7528\u7a0b\u5e8f\u5b9e\u73b0\u6a21\u62df\u7528\u6237\u767b\u5f55
\n \u603b\u5171\u7ed9\u4e09\u6b21\u673a\u4f1a，\u767b\u5f55\u4e4b\u540e，\u7ed9\u51fa\u76f8\u5e94\u7684\u63d0\u793a<\/p>\n

\u7b2c\u4e00\u4e2a\u65b9\u6cd5：\u4f7f\u7528equals
\n String username = "Yewen";
\n String rightUser = "yewen";
\n boolean b1 = username.equals(rightUser);
\n System.out.println(b1);
\n *\/<\/span>
\n \/\/1\u3001\u5df2\u77e5\u6b63\u786e\u7684\u7528\u6237\u540d\u548c\u5bc6\u7801<\/span>
\n String<\/span> rightUsername =<\/span> "Yewen"<\/span>;<\/span>
\n String<\/span> rightPassword =<\/span> "123456"<\/span>;<\/span><\/p>\n

\/\/\u603b\u5171\u7ed9\u4e09\u6b21\u673a\u4f1a<\/span>
\n for<\/span>(<\/span>int<\/span> i =<\/span> 0<\/span>;<\/span> i <<\/span> 3<\/span>;<\/span> i++<\/span>)<\/span>{<\/span>
\n \/\/2.\u8bf7\u7528\u7a0b\u5e8f\u5b9e\u73b0\u6a21\u62df\u7528\u6237\u767b\u5f55<\/span>
\n Scanner<\/span> s =<\/span> new<\/span> Scanner<\/span>(<\/span>System<\/span>.<\/span>in)<\/span>;<\/span>
\n System<\/span>.<\/span>out.<\/span>println<\/span>(<\/span>"\u8bf7\u8f93\u5165\u7528\u6237\u540d："<\/span>)<\/span>;<\/span>
\n String<\/span> username =<\/span> s.<\/span>next<\/span>(<\/span>)<\/span>;<\/span>
\n System<\/span>.<\/span>out.<\/span>println<\/span>(<\/span>"\u8bf7\u8f93\u5165\u5bc6\u7801："<\/span>)<\/span>;<\/span>
\n String<\/span> password =<\/span> s.<\/span>next<\/span>(<\/span>)<\/span>;<\/span>
\n \/\/3.\u6bd4\u8f83\u7528\u6237\u540d\u548c\u5bc6\u7801\u662f\u5426\u6b63\u786e<\/span>
\n boolean<\/span> result =<\/span> username.<\/span>equals<\/span>(<\/span>rightUsername)<\/span> &&<\/span> password.<\/span>equals<\/span>(<\/span>rightPassword)<\/span>;<\/span>
\n if<\/span>(<\/span>result)<\/span>{<\/span>
\n System<\/span>.<\/span>out.<\/span>println<\/span>(<\/span>"\u767b\u5f55\u6210\u529f！"<\/span>)<\/span>;<\/span>
\n break<\/span>;<\/span>
\n }<\/span>else<\/span>{<\/span>
\n if<\/span>(<\/span>i <<\/span> 2<\/span>)<\/span>{<\/span>
\n System<\/span>.<\/span>out.<\/span>println<\/span>(<\/span>"\u767b\u5f55\u5931\u8d25！\u8fd8\u5269\u4e0b"<\/span> +<\/span> (<\/span>2<\/span> –<\/span> i)<\/span> +<\/span> "\u6b21\u673a\u4f1a"<\/span>)<\/span>;<\/span>
\n }<\/span>else<\/span>{<\/span>
\n System<\/span>.<\/span>out.<\/span>println<\/span>(<\/span>"\u767b\u5f55\u5931\u8d25！\u8d26\u53f7\u5df2\u88ab\u9501\u5b9a"<\/span>)<\/span>;<\/span>
\n }<\/span>
\n }<\/span>
\n }<\/span>
\n }<\/span>
\n}<\/span><\/p>\n

📖\u4eca\u65e5\u77e5\u8bc6\u70b9 \u2014\u2014Java \u4e2d == \u53f7\u7684\u6bd4\u8f83\u89c4\u5219<\/h3>\n

\u6838\u5fc3\u7ed3\u8bba：<\/h4>\n

== \u53f7\u5728\u6bd4\u8f83\u4e0d\u540c\u6570\u636e\u7c7b\u578b\u65f6，\u5176\u542b\u4e49\u662f\u4e0d\u540c\u7684：<\/p>\n

  • \u57fa\u672c\u6570\u636e\u7c7b\u578b
    \n\u6bd4\u8f83\u5185\u5bb9：\u6bd4\u8f83\u7684\u662f\u6570\u636e\u503c\u3002<\/li>\n

    \u4ee3\u7801\u793a\u4f8b：<\/p>\n

    int<\/span> a =<\/span> 10<\/span>;<\/span>
    \nint<\/span> b =<\/span> 20<\/span>;<\/span>
    \nSystem<\/span>.<\/span>out.<\/span>println<\/span>(<\/span>a ==<\/span> b)<\/span>;<\/span> \/\/ \u8f93\u51fa false (\u56e0\u4e3a 10 \u4e0d\u7b49\u4e8e 20)<\/span><\/p>\n

  • \u5f15\u7528\u6570\u636e\u7c7b\u578b
    \n\u6bd4\u8f83\u5185\u5bb9：\u6bd4\u8f83\u7684\u662f\u5730\u5740\u503c\u3002<\/li>\n

    \u4ee3\u7801\u793a\u4f8b：<\/p>\n

    String<\/span> s1 =<\/span> new<\/span> String<\/span>(<\/span>"abc"<\/span>)<\/span>;<\/span>
    \nString<\/span> s2 =<\/span> new<\/span> String<\/span>(<\/span>"abc"<\/span>)<\/span>;<\/span>
    \nSystem<\/span>.<\/span>out.<\/span>println<\/span>(<\/span>s1 ==<\/span> s2)<\/span>;<\/span> \/\/ \u8f93\u51fa false (\u56e0\u4e3a s1 \u548c s2 \u662f\u4e24\u4e2a\u4e0d\u540c\u7684\u5bf9\u8c61，\u5185\u5b58\u5730\u5740\u4e0d\u540c)<\/span><\/p>\n

    (\u6ce8：\u867d\u7136\u4e24\u4e2a\u5b57\u7b26\u4e32\u5185\u5bb9\u90fd\u662f \u201cabc\u201d，\u4f46\u56e0\u4e3a\u4f7f\u7528\u4e86 new \u5173\u952e\u5b57，\u5b83\u4eec\u5728\u5806\u5185\u5b58\u4e2d\u662f\u4e0d\u540c\u7684\u5bf9\u8c61，\u5730\u5740\u503c\u4e0d\u540c)<\/p>\n

    📖\u4eca\u65e5\u77e5\u8bc6\u70b9 \u2014\u2014\u904d\u5386\u5b57\u7b26\u4e32<\/h3>\n

    public char charAt(int index)：\u6839\u636e\u7d22\u5f15\u8fd4\u56de\u5b57\u7b26<\/p>\n

    public int length()：\u8fd4\u56de\u6b64\u5b57\u7b26\u4e32\u7684\u957f\u5ea6<\/p>\n

    \u6570\u7ec4\u7684\u957f\u5ea6：\u6570\u7ec4\u540d.length<\/p>\n

    \u5b57\u7b26\u4e32\u7684\u957f\u5ea6：\u5b57\u7b26\u4e32\u5bf9\u8c61.length()<\/p>\n

    💻\u7ec3\u4e60\u4ee3\u7801<\/h3>\n

    package<\/span> com.<\/span>itheima.<\/span>apidemo4<\/span>;<\/span><\/p>\n

    import<\/span> java.<\/span>util.<\/span><\/span>Scanner<\/span><\/span>;<\/span><\/p>\n

    public<\/span> class<\/span> Test<\/span> {<\/span>
    \n public<\/span> static<\/span> void<\/span> main<\/span>(<\/span>String<\/span>[<\/span>]<\/span> args)<\/span>{<\/span>
    \n \/*
    \n \u6b63\u6587\u5185\u5bb9：
    \n \u9700\u6c42：\u952e\u76d8\u5f55\u5165\u4e00\u4e2a\u5b57\u7b26\u4e32，\u4f7f\u7528\u7a0b\u5e8f\u5b9e\u73b0\u5728\u63a7\u5236\u53f0\u904d\u5386\u8be5\u5b57\u7b26\u4e32<\/p>\n

    public char charAt(int index)：\u6839\u636e\u7d22\u5f15\u8fd4\u56de\u5b57\u7b26
    \n public int length()：\u8fd4\u56de\u6b64\u5b57\u7b26\u4e32\u7684\u957f\u5ea6
    \n \u6570\u7ec4\u7684\u957f\u5ea6：\u6570\u7ec4\u540d.length
    \n \u5b57\u7b26\u4e32\u7684\u957f\u5ea6：\u5b57\u7b26\u4e32\u5bf9\u8c61.length()
    \n *\/<\/span><\/p>\n

    \/\/\u6839\u636e\u7d22\u5f15\u8fd4\u56de\u5b57\u7b26<\/span>
    \n String<\/span> str =<\/span> "Yewen0625"<\/span>;<\/span>
    \n char<\/span> c =<\/span> str.<\/span>charAt<\/span>(<\/span>4<\/span>)<\/span>;<\/span>
    \n System<\/span>.<\/span>out.<\/span>println<\/span>(<\/span>c)<\/span>;<\/span>\/\/n<\/span>
    \n \/\/\u83b7\u53d6\u5b57\u7b26\u4e32\u7684\u957f\u5ea6<\/span>
    \n int<\/span> length =<\/span> str.<\/span>length<\/span>(<\/span>)<\/span>;<\/span>
    \n System<\/span>.<\/span>out.<\/span>println<\/span>(<\/span>length)<\/span>;<\/span>\/\/9<\/span>
    \n \/\/\u952e\u76d8\u5f55\u5165\u4e00\u4e2a\u5b57\u7b26\u4e32，\u4f7f\u7528\u7a0b\u5e8f\u5b9e\u73b0\u5728\u63a7\u5236\u53f0\u904d\u5386\u8be5\u5b57\u7b26\u4e32<\/span>
    \n Scanner<\/span> sc =<\/span> new<\/span> Scanner<\/span>(<\/span>System<\/span>.<\/span>in)<\/span>;<\/span>
    \n System<\/span>.<\/span>out.<\/span>println<\/span>(<\/span>"\u8bf7\u8f93\u5165\u4e00\u4e2a\u5b57\u7b26\u4e32："<\/span>)<\/span>;<\/span>
    \n String<\/span> s =<\/span> sc.<\/span>next<\/span>(<\/span>)<\/span>;<\/span>
    \n \/\/\u5b57\u7b26\u4e32\u904d\u5386\u4e2d\u5faa\u73af\u7684\u5feb\u901f\u751f\u6210\u65b9\u5f0fs.length().fori<\/span>
    \n for<\/span> (<\/span>int<\/span> i =<\/span> 0<\/span>;<\/span> i <<\/span> s.<\/span>length<\/span>(<\/span>)<\/span>;<\/span> i++<\/span>)<\/span> {<\/span>
    \n char<\/span> cc =<\/span> s.<\/span>charAt<\/span>(<\/span>i)<\/span>;<\/span>
    \n System<\/span>.<\/span>out.<\/span>println<\/span>(<\/span>cc)<\/span>;<\/span>
    \n }<\/span><\/p>\n

    }<\/span>
    \n}<\/span><\/p>\n

    \u7edf\u8ba1\u5b57\u7b26\u6b21\u6570<\/p>\n

    package<\/span> com.<\/span>itheima.<\/span>apidemo4<\/span>;<\/span><\/p>\n

    import<\/span> java.<\/span>util.<\/span><\/span>Scanner<\/span><\/span>;<\/span><\/p>\n

    public<\/span> class<\/span> Test2<\/span> {<\/span>
    \n public<\/span> static<\/span> void<\/span> main<\/span>(<\/span>String<\/span>[<\/span>]<\/span> args)<\/span> {<\/span>
    \n \/*
    \n \u952e\u76d8\u5f55\u5165\u4e00\u4e2a\u5b57\u7b26\u4e32，\u7edf\u8ba1\u8be5\u5b57\u7b26\u4e32\u4e2d\u5927\u5c0f\u5199\u7684\u5b57\u6bcd\u5b57\u7b26，\u5c0f\u5199\u5b57\u6bcd\u5b57\u7b26，
    \n \u6570\u5b57\u5b57\u7b26\u51fa\u73b0\u7684\u6b21\u6570（\u4e0d\u8003\u8651\u5176\u4ed6\u5b57\u7b26）
    \n *\/<\/span>
    \n \/\/1.\u952e\u76d8\u5f55\u5165\u4e00\u4e2a\u5b57\u7b26\u4e32<\/span>
    \n Scanner<\/span> sc =<\/span> new<\/span> Scanner<\/span>(<\/span>System<\/span>.<\/span>in)<\/span>;<\/span>
    \n System<\/span>.<\/span>out.<\/span>println<\/span>(<\/span>"\u8bf7\u8f93\u5165\u4e00\u4e2a\u5b57\u7b26\u4e32："<\/span>)<\/span>;<\/span>
    \n String<\/span> str =<\/span> sc.<\/span>next<\/span>(<\/span>)<\/span>;<\/span>
    \n \/\/2.\u904d\u5386\u5b57\u7b26\u4e32\u5f97\u5230\u6bcf\u4e00\u4e2a\u5b57\u7b26<\/span>
    \n \/\/3.\u8ba1\u6570\u5668\u601d\u60f3 count<\/span>
    \n int<\/span> upperCount =<\/span> 0<\/span>;<\/span>\/\/\u5927\u5199\u5b57\u6bcd<\/span>
    \n int<\/span> lowerCount =<\/span> 0<\/span>;<\/span>\/\/\u5c0f\u5199\u5b57\u6bcd<\/span>
    \n int<\/span> numberCount =<\/span> 0<\/span>;<\/span>\/\/\u6570\u5b57<\/span>
    \n for<\/span> (<\/span>int<\/span> i =<\/span> 0<\/span>;<\/span> i <<\/span> str.<\/span>length<\/span>(<\/span>)<\/span>;<\/span> i++<\/span>)<\/span> {<\/span>
    \n char<\/span> c =<\/span> str.<\/span>charAt<\/span>(<\/span>i)<\/span>;<\/span>
    \n if<\/span> (<\/span>c >=<\/span> 'A'<\/span> &&<\/span> c <=<\/span> 'Z'<\/span>)<\/span> {<\/span>
    \n upperCount++<\/span>;<\/span>
    \n }<\/span> else<\/span> if<\/span> (<\/span>c >=<\/span> 'a'<\/span> &&<\/span> c <=<\/span> 'z'<\/span>)<\/span> {<\/span>
    \n lowerCount++<\/span>;<\/span>
    \n }<\/span> else<\/span> if<\/span> (<\/span>c >=<\/span> '0'<\/span> &&<\/span> c <=<\/span> '9'<\/span>)<\/span> {<\/span>
    \n numberCount++<\/span>;<\/span>
    \n }<\/span>else<\/span>{<\/span>
    \n System<\/span>.<\/span>out.<\/span>println<\/span>(<\/span>"\u5176\u4ed6\u5b57\u7b26\u4e0d\u53c2\u4e0e\u7edf\u8ba1"<\/span>)<\/span>;<\/span>
    \n break<\/span>;<\/span>
    \n }<\/span>
    \n }<\/span>
    \n \/\/4.\u6253\u5370<\/span>
    \n System<\/span>.<\/span>out.<\/span>println<\/span>(<\/span>"\u5927\u5199\u5b57\u6bcd\u51fa\u73b0\u7684\u6b21\u6570\u662f："<\/span> +<\/span> upperCount)<\/span>;<\/span>
    \n System<\/span>.<\/span>out.<\/span>println<\/span>(<\/span>"\u5c0f\u5199\u5b57\u6bcd\u51fa\u73b0\u7684\u6b21\u6570\u662f："<\/span> +<\/span> lowerCount)<\/span>;<\/span>
    \n System<\/span>.<\/span>out.<\/span>println<\/span>(<\/span>"\u6570\u5b57\u51fa\u73b0\u7684\u6b21\u6570\u662f："<\/span> +<\/span> numberCount)<\/span>;<\/span>
    \n }<\/span>
    \n}<\/span><\/p>\n

    \u62fc\u63a5\u5b57\u7b26\u4e32<\/p>\n

    package<\/span> com.<\/span>itheima.<\/span>apidemo4<\/span>;<\/span><\/p>\n

    public<\/span> class<\/span> Test3<\/span> {<\/span>
    \n public<\/span> static<\/span> void<\/span> main<\/span>(<\/span>String<\/span>[<\/span>]<\/span> args)<\/span> {<\/span>
    \n \/*
    \n \u5b9a\u4e49\u4e00\u4e2a\u65b9\u6cd5，\u628a int \u6570\u7ec4\u4e2d\u7684\u6570\u636e\u6309\u7167\u6307\u5b9a\u7684\u683c\u5f0f\u62fc\u63a5\u6210\u4e00\u4e2a\u5b57\u7b26\u4e32\u8fd4\u56de，
    \n \u8c03\u7528\u8be5\u65b9\u6cd5，\u5e76\u5728\u63a7\u5236\u53f0\u8f93\u51fa\u7ed3\u679c\u3002
    \n \u4f8b\u5982：
    \n \u6570\u7ec4\u4e3a int[] arr = {1,2,3};
    \n \u6267\u884c\u65b9\u6cd5\u540e\u7684\u8f93\u51fa\u7ed3\u679c\u4e3a：[1, 2, 3]
    \n *\/<\/span>
    \n \/\/1\u3001\u5b9a\u4e49\u4e00\u4e2a\u6570\u7ec4<\/span>
    \n int<\/span>[<\/span>]<\/span> arr =<\/span> {<\/span>1<\/span>,<\/span> 2<\/span>,<\/span> 3<\/span>}<\/span>;<\/span>
    \n \/\/2\u3001\u8c03\u7528\u65b9\u6cd5\u5e76\u6253\u5370\u7ed3\u679c<\/span>
    \n System<\/span>.<\/span>out.<\/span>println<\/span>(<\/span>arrayToString<\/span>(<\/span>arr)<\/span>)<\/span>;<\/span>
    \n }<\/span>
    \n public<\/span> static<\/span> String<\/span> arrayToString<\/span>(<\/span>int<\/span>[<\/span>]<\/span> arr)<\/span> {<\/span>
    \n String<\/span> result =<\/span> "["<\/span>;<\/span>
    \n for<\/span> (<\/span>int<\/span> i =<\/span> 0<\/span>;<\/span> i <<\/span> arr.<\/span>length;<\/span> i++<\/span>)<\/span> {<\/span>
    \n if<\/span>(<\/span>i ==<\/span> arr.<\/span>length –<\/span> 1<\/span>)<\/span>{<\/span>
    \n result +=<\/span> arr[<\/span>i]<\/span>;<\/span>
    \n }<\/span>else<\/span>{<\/span>
    \n result +=<\/span> arr[<\/span>i]<\/span> +<\/span> ", "<\/span>;<\/span>
    \n }<\/span>
    \n }<\/span>
    \n result +=<\/span> "]"<\/span>;<\/span>
    \n return<\/span> result;<\/span>
    \n }<\/span>
    \n }<\/span><\/p>\n

    📖\u4eca\u65e5\u77e5\u8bc6\u70b9 \u2014\u2014\u5b57\u7b26\u4e32\u7684\u622a\u53d6\u3001\u66ff\u6362\u548c\u5176\u4ed6\u5e38\u89c1\u65b9\u6cd5——-\u6570\u636e\u8131\u654f<\/h3>\n

    1\u3001String substring(int beginIndex, int endIndex) \u622a\u53d6<\/h5>\n

    \u6ce8\u610f\u70b9：\u5305\u5934\u4e0d\u5305\u5c3e，\u5305\u5de6\u4e0d\u5305\u53f3<\/p>\n

    \u53ea\u6709\u8fd4\u56de\u503c\u624d\u662f\u622a\u53d6\u7684\u5c0f\u4e32<\/p>\n

    2\u3001String substring(int beginIndex) \u622a\u53d6\u5230\u672b\u5c3e<\/h5>\n

    💻\u7ec3\u4e60\u4ee3\u7801<\/h3>\n

    package<\/span> com.<\/span>itheima.<\/span>apidemo5<\/span>;<\/span><\/p>\n

    public<\/span> class<\/span> Test1<\/span> {<\/span>
    \n public<\/span> static<\/span> void<\/span> main<\/span>(<\/span>String<\/span>[<\/span>]<\/span> args)<\/span> {<\/span>
    \n \/*
    \n public String substring(int beginIndex, int endIndex): \u622a\u53d6\u6307\u5b9a\u8303\u56f4
    \n public String substring(int beginIndex): \u622a\u53d6\u5230\u672b\u5c3e<\/p>\n

    \u9700\u6c42：\u53ea\u4fdd\u7559\u7528\u6237\u540d\u7684\u7b2c\u4e00\u4e2a\u5b57\u7b26，\u540e\u9762\u7528\u4e09\u4e2a***\u66ff\u4ee3
    \n *\/<\/span><\/p>\n

    \/\/ \u5b9a\u4e49\u4e00\u4e2a\u5b57\u7b26\u4e32<\/span>
    \n String<\/span> str =<\/span> "abcdef"<\/span>;<\/span>
    \n \/\/ \u622a\u53d6<\/span>
    \n \/\/ \u7b2c\u4e00\u4e2a\u53c2\u6570：\u622a\u53d6\u7684\u5f00\u59cb\u7d22\u5f15<\/span>
    \n \/\/ \u7b2c\u4e8c\u4e2a\u53c2\u6570：\u622a\u53d6\u7684\u672b\u5c3e\u7d22\u5f15<\/span>
    \n \/\/ \u5305\u5934\u4e0d\u5305\u5c3e，\u5305\u5de6\u4e0d\u5305\u53f3 —-> \u5305\u542b1\u7d22\u5f15，\u4f46\u662f\u4e0d\u5305\u542b5\u7d22\u5f15 1 2 3 4<\/span>
    \n \/\/ \u5b57\u7b26\u4e32\u672c\u8eab\u4e00\u65e6\u521b\u5efa\u4e4b\u540e，\u662f\u65e0\u6cd5\u53d1\u73b0\u6539\u53d8\u7684，\u622a\u53d6\u7684\u65f6\u5019\u4e0d\u4f1a\u5f71\u54cd\u8c03\u7528\u8005\u7684\u5b57\u7b26\u4e32，\u5207\u8bb0：\u53ea\u6709\u8fd4\u56de\u503c\u624d\u662f\u622a\u53d6\u4e4b\u540e\u7684\u7ed3\u679c<\/span>
    \n String<\/span> res =<\/span> str.<\/span>substring<\/span>(<\/span>1<\/span>,<\/span>5<\/span>)<\/span>;<\/span>\/\/bcde<\/span>
    \n System<\/span>.<\/span>out.<\/span>println<\/span>(<\/span>res)<\/span>;<\/span>
    \n \/\/ \u53c2\u6570：\u622a\u53d6\u7684\u5f00\u59cb\u7d22\u5f15，\u9ed8\u8ba4\u662f\u622a\u53d6\u5230\u5b57\u7b26\u4e32\u7684\u672b\u5c3e<\/span>
    \n \/\/ \u5b57\u7b26\u4e32\u672c\u8eab\u4e00\u65e6\u521b\u5efa\u4e4b\u540e，\u662f\u65e0\u6cd5\u53d1\u73b0\u6539\u53d8\u7684，\u622a\u53d6\u7684\u65f6\u5019\u4e0d\u4f1a\u5f71\u54cd\u8c03\u7528\u8005\u7684\u5b57\u7b26\u4e32，\u5207\u8bb0：\u53ea\u6709\u8fd4\u56de\u503c\u624d\u662f\u622a\u53d6\u4e4b\u540e\u7684\u7ed3\u679c<\/span>
    \n String<\/span> res2 =<\/span> str.<\/span>substring<\/span>(<\/span>1<\/span>)<\/span>;<\/span>\/\/bcddef<\/span>
    \n System<\/span>.<\/span>out.<\/span>println<\/span>(<\/span>res2)<\/span>;<\/span>
    \n System<\/span>.<\/span>out.<\/span>println<\/span>(<\/span>"======================================"<\/span> )<\/span>;<\/span>
    \n \/\/\u7ec3\u4e60：\u9700\u6c42：\u53ea\u4fdd\u7559\u7528\u6237\u540d\u7684\u7b2c\u4e00\u4e2a\u5b57\u7b26，\u540e\u9762\u7528\u4e09\u4e2a***\u66ff\u4ee3<\/span>
    \n \/\/charAt(0)\u83b7\u53d6\u7b2c\u4e00\u4e2a\u5b57\u7b26<\/span>
    \n \/\/substring(0,1)\u622a\u53d6\u4ece\u7d22\u5f150\u5f00\u59cb\u5230\u7d22\u5f151\u7ed3\u675f<\/span>
    \n String<\/span> username =<\/span> "\u6545\u4eba\u897f\u8f9e"<\/span>;<\/span>
    \n \/\/ctrl+alt+v\u81ea\u52a8\u751f\u6210\u5de6\u8fb9<\/span>
    \n char<\/span> firstName1 =<\/span> username.<\/span>charAt<\/span>(<\/span>0<\/span>)<\/span>;<\/span>
    \n String<\/span> result1 =<\/span> firstName1 +<\/span> "***"<\/span>;<\/span>
    \n System<\/span>.<\/span>out.<\/span>println<\/span>(<\/span>result1)<\/span>;<\/span>
    \n String<\/span> firstName2 =<\/span> username.<\/span>substring<\/span>(<\/span>0<\/span>,<\/span>1<\/span>)<\/span>;<\/span>
    \n String<\/span> result2 =<\/span> firstName2 +<\/span> "***"<\/span>;<\/span>
    \n System<\/span>.<\/span>out.<\/span>println<\/span>(<\/span>result2)<\/span>;<\/span><\/p>\n

    }<\/span>
    \n}<\/span><\/p>\n

    📖\u4eca\u65e5\u77e5\u8bc6\u70b9 \u2014\u2014\u5b57\u7b26\u4e32\u7684\u622a\u53d6\u3001\u66ff\u6362\u548c\u5176\u4ed6\u5e38\u89c1\u65b9\u6cd5——-\u654f\u611f\u8bcd\u8fc7\u6ee4<\/h3>\n

    String replace(\u65e7\u503c,\u65b0\u503c) \u66ff\u6362<\/h5>\n

    \u6ce8\u610f\u70b9：\u53ea\u6709\u8fd4\u56de\u503c\u624d\u662f\u66ff\u6362\u4e4b\u540e\u7684\u7ed3\u679c<\/p>\n

    \n

    subString\u622a\u53d6：\u622a\u53d6\u56fa\u5b9a\u4f4d\u7f6e\u7684\u6570\u636e<\/p>\n

    replac\u66ff\u6362：\u4f4d\u7f6e\u4e0d\u786e\u5b9a，\u66ff\u6362\u6307\u5b9a\u5185\u5bb9<\/p>\n

    💻\u7ec3\u4e60\u4ee3\u7801<\/h3>\n

    package<\/span> com.<\/span>itheima.<\/span>apidemo5<\/span>;<\/span><\/p>\n

    import<\/span> java.<\/span>util.<\/span><\/span>Scanner<\/span><\/span>;<\/span><\/p>\n

    public<\/span> class<\/span> Test2<\/span> {<\/span>
    \n public<\/span> static<\/span> void<\/span> main<\/span>(<\/span>String<\/span>[<\/span>]<\/span> args)<\/span>{<\/span>
    \n \/*
    \n String replace(\u65e7\u503c,\u65b0\u503c) \u66ff\u6362
    \n \u6ce8\u610f\u70b9：\u53ea\u6709\u8fd4\u56de\u503c\u624d\u662f\u66ff\u6362\u4e4b\u540e\u7684\u7ed3\u679c<\/p>\n

    \u9700\u6c42：
    \n \u8fc7\u6ee4\u73a9\u6e38\u620f\u4e2d\u7684\u9a82\u4eba\u7684\u810f\u8bdd
    \n *\/<\/span>
    \n \/\/ \u5b9a\u4e49\u5b57\u7b26\u4e32<\/span>
    \n \/\/String str = "\u4f60\u73a9\u7684\u597d\u83dc\u5440，TMD";<\/span>
    \n \/\/ \u66ff\u6362<\/span>
    \n \/\/ \u7b2c\u4e00\u4e2a\u53c2\u6570：\u88ab\u66ff\u6362\u7684\u6570\u636e<\/span>
    \n \/\/ \u7b2c\u4e8c\u4e2a\u53c2\u6570：\u7528\u6765\u66ff\u6362\u7684\u6570\u636e<\/span>
    \n \/\/ \u53ea\u6709\u8fd4\u56de\u503c\u624d\u4f1a\u66ff\u6362\u4e4b\u540e\u7684\u7ed3\u679c<\/span>
    \n \/\/String res = str.replace("TMD","****");<\/span>
    \n \/\/System.out.println(res);<\/span><\/p>\n

    \/\/1.\u5b9a\u4e49\u4e00\u4e2a\u654f\u611f\u8bcd\u5e93<\/span>
    \n String<\/span>[<\/span>]<\/span> arr =<\/span> {<\/span>"TMD"<\/span>,<\/span>"SB"<\/span>,<\/span>"jr"<\/span>,<\/span>"ck"<\/span>}<\/span>;<\/span>
    \n \/\/2.\u952e\u76d8\u5f55\u5165\u4e00\u4e2a\u5b57\u7b26\u4e32<\/span>
    \n Scanner<\/span> sc =<\/span> new<\/span> Scanner<\/span>(<\/span>System<\/span>.<\/span>in)<\/span>;<\/span>
    \n System<\/span>.<\/span>out.<\/span>println<\/span>(<\/span>"\u8bf7\u8f93\u5165\u4e00\u4e2a\u5b57\u7b26\u4e32："<\/span>)<\/span>;<\/span>
    \n String<\/span> msg =<\/span> sc.<\/span>next<\/span>(<\/span>)<\/span>;<\/span>
    \n \/\/3.\u66ff\u6362\u654f\u611f\u8bcd<\/span>
    \n for<\/span> (<\/span>int<\/span> i =<\/span> 0<\/span>;<\/span> i <<\/span> arr.<\/span>length;<\/span> i++<\/span>)<\/span> {<\/span>
    \n \/\/arr[i]:\u4f9d\u6b21\u8868\u793a\u654f\u611f\u8bcd\u5e93\u4e2d\u7684\u6bcf\u4e00\u4e2a\u654f\u611f\u8bcd<\/span>
    \n msg =<\/span> msg.<\/span>replace<\/span>(<\/span>arr[<\/span>i]<\/span>,<\/span>"***"<\/span>)<\/span>;<\/span>
    \n }<\/span>
    \n System<\/span>.<\/span>out.<\/span>println<\/span>(<\/span>msg)<\/span>;<\/span><\/p>\n

    }<\/span>
    \n}<\/span><\/p>\n

    📖\u4eca\u65e5\u77e5\u8bc6\u70b9 \u2014\u2014\u5b57\u7b26\u4e32\u7684\u5176\u4ed6\u5e38\u89c1\u65b9\u6cd5<\/h3>\n

    \u6bd4\u8f83：equals equalsIgnoreCase<\/p>\n

    \u957f\u5ea6：length<\/p>\n

    \u83b7\u53d6\u5355\u4e2a\u5b57\u7b26：charAt<\/p>\n

    \u622a\u53d6：substring<\/p>\n

    \u66ff\u6362：replace<\/p>\n

    💻\u7ec3\u4e60\u4ee3\u7801<\/h3>\n

    package<\/span> com.<\/span>itheima.<\/span>apidemo5<\/span>;<\/span><\/p>\n

    import<\/span> java.<\/span>util.<\/span><\/span>Locale<\/span><\/span>;<\/span><\/p>\n

    public<\/span> class<\/span> Test3<\/span> {<\/span>
    \n public<\/span> static<\/span> void<\/span> main<\/span>(<\/span>String<\/span>[<\/span>]<\/span> args)<\/span> {<\/span>
    \n \/*
    \n String \u7c7b\u5f53\u4e2d\u5e38\u89c1\u7684\u65b9\u6cd5：
    \n \u6bd4\u8f83 equals equalsIgnoreCase
    \n \u957f\u5ea6 length
    \n \u83b7\u53d6\u5355\u4e2a\u5b57\u7b26 charAt
    \n \u622a\u53d6 substring
    \n \u66ff\u6362 replace<\/p>\n

    \u662f\u5426\u5305\u542b contains
    \n \u5224\u65ad\u5f00\u5934\u3001\u7ed3\u5c3e startsWith\/endsWith
    \n \u67e5\u627e indexOf(int ch) lastIndexOf(int ch)
    \n \u5224\u65ad\u662f\u5426\u4e3a\u7a7a isEmpty()
    \n \u8f6c\u5b57\u7b26\u6570\u7ec4 toCharArray()
    \n \u5927\u5c0f\u5199\u8f6c\u6362 toUpperCase() \u3001toLowerCase()
    \n \u53bb\u9664\u5934\u5c3e\u7a7a\u683c trim()<\/p>\n

    *\/<\/span>
    \n String<\/span> str =<\/span> "abcdefgd"<\/span>;<\/span>
    \n \/\/\u662f\u5426\u5305\u542bcontains—\u654f\u611f\u8bcd\u8fc7\u6ee4<\/span>
    \n boolean<\/span> b1 =<\/span> str.<\/span>contains<\/span>(<\/span>"abd"<\/span>)<\/span>;<\/span>
    \n System<\/span>.<\/span>out.<\/span>println<\/span>(<\/span>b1)<\/span>;<\/span>\/\/false<\/span><\/p>\n

    \/\/\u5224\u65ad\u5f00\u5934\u3001\u7ed3\u5c3e startsWith\/endsWith<\/span>
    \n \/\/\u5224\u65ad\u6587\u4ef6\u540e\u7f00\u540d a.txt<\/span>
    \n boolean<\/span> b2 =<\/span> str.<\/span>startsWith<\/span>(<\/span>"bc"<\/span>)<\/span>;<\/span>\/\/\u5224\u65ad\u662f\u5426\u4ee5bc\u5f00\u5934<\/span>
    \n System<\/span>.<\/span>out.<\/span>println<\/span>(<\/span>b2)<\/span>;<\/span>\/\/false<\/span>
    \n boolean<\/span> b3 =<\/span> str.<\/span>startsWith<\/span>(<\/span>"bc"<\/span>,<\/span>1<\/span>)<\/span>;<\/span>\/\/\u4ece\u7d22\u5f151\u5f00\u59cb\u5224\u65ad\u662f\u5426\u4ee5abc\u5f00\u5934<\/span>
    \n System<\/span>.<\/span>out.<\/span>println<\/span>(<\/span>b3)<\/span>;<\/span>\/\/true<\/span><\/p>\n

    boolean<\/span> b4 =<\/span> str.<\/span>endsWith<\/span>(<\/span>".txt"<\/span>)<\/span>;<\/span>
    \n System<\/span>.<\/span>out.<\/span>println<\/span>(<\/span>b4)<\/span>;<\/span>\/\/false<\/span><\/p>\n

    \/\/\u67e5\u627e indexOf(int ch) lastIndexOf(int ch)—\u6700\u540e\u4e00\u6b21\u51fa\u73b0\u7684\u7d22\u5f15<\/span>
    \n \/\/\u67e5\u627e\u5f53\u524d\u5b57\u7b26\/\u5b57\u7b26\u4e32 \u7b2c\u4e00\u6b21\u51fa\u73b0\u7684\u7d22\u5f15,\u5982\u679c\u5f53\u524d\u67e5\u627e\u7684\u5185\u5bb9\u4e0d\u5b58\u5728，\u65b9\u6cd5\u4f1a\u8fd4\u56de-1<\/span>
    \n int<\/span> i1 =<\/span> str.<\/span>indexOf<\/span>(<\/span>99<\/span>)<\/span>;<\/span>
    \n System<\/span>.<\/span>out.<\/span>println<\/span>(<\/span>i1)<\/span>;<\/span>\/\/2<\/span>
    \n int<\/span> i2 =<\/span> str.<\/span>lastIndexOf<\/span>(<\/span>100<\/span>)<\/span>;<\/span>
    \n System<\/span>.<\/span>out.<\/span>println<\/span>(<\/span>i2)<\/span>;<\/span>\/\/7<\/span>
    \n int<\/span> i3 =<\/span> str.<\/span>indexOf<\/span>(<\/span>104<\/span>)<\/span>;<\/span>
    \n System<\/span>.<\/span>out.<\/span>println<\/span>(<\/span>i3)<\/span>;<\/span>\/\/-1<\/span><\/p>\n

    \/\/\u5224\u65ad\u662f\u5426\u4e3a\u7a7a isEmpty()<\/span>
    \n boolean<\/span> empty1 =<\/span> str.<\/span>isEmpty<\/span>(<\/span>)<\/span>;<\/span>
    \n System<\/span>.<\/span>out.<\/span>println<\/span>(<\/span>empty1)<\/span>;<\/span>\/\/false<\/span><\/p>\n

    String<\/span> str2 =<\/span> ""<\/span>;<\/span>
    \n boolean<\/span> empty2 =<\/span> str2.<\/span>isEmpty<\/span>(<\/span>)<\/span>;<\/span>
    \n System<\/span>.<\/span>out.<\/span>println<\/span>(<\/span>empty2)<\/span>;<\/span>\/\/true<\/span><\/p>\n

    \/\/\u8f6c\u5b57\u7b26\u6570\u7ec4 toCharArray()<\/span>
    \n \/\/\u5c06\u5b57\u7b26\u4e32\u8f6c\u6362\u4e3a\u5b57\u7b26\u6570\u7ec4<\/span>
    \n \/\/"abcdefgd"—->['a','b','c','d','e','f','g','d']<\/span>
    \n \/\/"abc"—>0\u7d22\u5f15\u6539\u4e3aA，\u5c31\u53ef\u4ee5\u7528\u5230toCharArray()\u5148\u5c06\u5b57\u7b26\u4e32\u8f6c\u6362\u4e3a\u5b57\u7b26\u6570\u7ec4，\u518d\u5c060\u7d22\u5f15\u6539\u4e3aA<\/span>
    \n char<\/span>[<\/span>]<\/span> array =<\/span> str.<\/span>toCharArray<\/span>(<\/span>)<\/span>;<\/span>
    \n for<\/span> (<\/span>int<\/span> i =<\/span> 0<\/span>;<\/span> i <<\/span> array.<\/span>length;<\/span> i++<\/span>)<\/span> {<\/span>
    \n System<\/span>.<\/span>out.<\/span>println<\/span>(<\/span>array[<\/span>i]<\/span>)<\/span>;<\/span>
    \n }<\/span><\/p>\n

    \/\/\u5927\u5c0f\u5199\u8f6c\u6362 toUpperCase() \u3001toLowerCase()<\/span>
    \n \/\/\u53ea\u80fd\u8f6c\u6362\u5b57\u7b26\u4e32\u4e2d\u7684\u82f1\u6587，\u4e0d\u80fd\u8f6c\u6362\u4e2d\u6587<\/span>
    \n String<\/span> upperCase =<\/span> str.<\/span>toUpperCase<\/span>(<\/span>Locale<\/span>.<\/span>ROOT<\/span>)<\/span>;<\/span>
    \n System<\/span>.<\/span>out.<\/span>println<\/span>(<\/span>upperCase)<\/span>;<\/span>\/\/ABCDEFGD<\/span><\/p>\n

    String<\/span> str1 =<\/span> "ABC"<\/span>;<\/span>
    \n String<\/span> lowerCase =<\/span> str1.<\/span>toLowerCase<\/span>(<\/span>Locale<\/span>.<\/span>ROOT<\/span>)<\/span>;<\/span>
    \n System<\/span>.<\/span>out.<\/span>println<\/span>(<\/span>lowerCase)<\/span>;<\/span>\/\/abc<\/span><\/p>\n

    \/\/\u53bb\u9664\u5934\u5c3e\u7a7a\u683c trim()<\/span>
    \n String<\/span> str3 =<\/span> " abc "<\/span>;<\/span>
    \n String<\/span> trim =<\/span> str3.<\/span>trim<\/span>(<\/span>)<\/span>;<\/span>
    \n System<\/span>.<\/span>out.<\/span>println<\/span>(<\/span>trim)<\/span>;<\/span>\/\/"abc"<\/span>
    \n }<\/span>
    \n}<\/span><\/p>\n

    📖\u4eca\u65e5\u77e5\u8bc6\u70b9 \u2014\u2014StringBuilder<\/h3>\n

    StringBuilder append (\u4efb\u610f\u7c7b\u578b)\u6dfb\u52a0\u6570\u636e
    \nStringBuilder reverse() \u53cd\u8f6c\u5bb9\u5668\u4e2d\u7684\u5185\u5bb9
    \nint length()\u8fd4\u56de\u957f\u5ea6 （\u5b57\u7b26\u7684\u4e2a\u6570）
    \nString toString() \u8f6c\u56deString\u5b57\u7b26\u4e32\u5bf9\u8c61<\/p>\n

    StringBuilder \u6784\u9020\u65b9\u6cd5<\/h5>\n

    \u6784\u9020\u65b9\u6cd5 \u8bf4\u660e
    \npublic StringBuilder() \u521b\u5efaStringBuilder\u5bb9\u5668，\u4e0d\u542b\u6709\u4efb\u4f55\u5185\u5bb9
    \npublic StringBuilder(String str)\u521b\u5efaStringBuilder\u5bb9\u5668，\u5305\u542b\u6307\u5b9a\u7684\u5185\u5bb9<\/p>\n

    💻\u7ec3\u4e60\u4ee3\u7801<\/h3>\n

    package<\/span> com.<\/span>itheima.<\/span>stringbuilderdemo6<\/span>;<\/span><\/p>\n

    public<\/span> class<\/span> Test3<\/span> {<\/span>
    \n public<\/span> static<\/span> void<\/span> main<\/span>(<\/span>String<\/span>[<\/span>]<\/span> args)<\/span> {<\/span>
    \n \/*
    \n StringBuilder\u7684\u6784\u9020\u65b9\u6cd5：
    \n public StringBuilder() \u7a7a\u53c2\u6784\u9020
    \n public StringBuilder(String str) \u5e26\u53c2\u6784\u9020<\/p>\n

    StringBuilder\u7684\u5e38\u89c1\u6210\u5458\u65b9\u6cd5：
    \n append (\u4efb\u610f\u7c7b\u578b) \u6dfb\u52a0\u6570\u636e
    \n reverse() \u53cd\u8f6c
    \n int length() \u83b7\u53d6\u957f\u5ea6
    \n toString \u53d8\u56de\u5b57\u7b26\u4e32<\/p>\n

    *\/<\/span>
    \n \/\/1.\u521b\u5efaStringBuilder\u5bf9\u8c61（\u5bb9\u5668） \u7a7a\u53c2\u6784\u9020<\/span>
    \n StringBuilder<\/span> sb1 =<\/span> new<\/span> StringBuilder<\/span>(<\/span>)<\/span>;<\/span>
    \n System<\/span>.<\/span>out.<\/span>println<\/span>(<\/span>"==="<\/span> +<\/span> sb1 +<\/span> "&&&"<\/span>)<\/span>;<\/span>
    \n int<\/span> len =<\/span> sb1.<\/span>length<\/span>(<\/span>)<\/span>;<\/span>
    \n System<\/span>.<\/span>out.<\/span>println<\/span>(<\/span>"len:"<\/span> +<\/span> len)<\/span>;<\/span>\/\/0<\/span>
    \n \/\/2.\u521b\u5efaStringBuilder\u5bf9\u8c61（\u5bb9\u5668） \u5e26\u53c2\u6784\u9020<\/span>
    \n StringBuilder<\/span> sb2 =<\/span> new<\/span> StringBuilder<\/span>(<\/span>"hello"<\/span>)<\/span>;<\/span>
    \n \/\/\u6dfb\u52a0<\/span>
    \n \/\/sb2.append("Yewen");<\/span>
    \n \/\/System.out.println(sb2);\/\/helloYewen<\/span>
    \n \/\/\u53cd\u8f6c<\/span>
    \n sb2.<\/span>reverse<\/span>(<\/span>)<\/span>;<\/span>
    \n System<\/span>.<\/span>out.<\/span>println<\/span>(<\/span>sb2)<\/span>;<\/span>\/\/olleh<\/span>
    \n \/\/\u8f6c\u6362\u4e3a\u5b57\u7b26\u4e32<\/span>
    \n String<\/span> res =<\/span> sb2.<\/span>toString<\/span>(<\/span>)<\/span>;<\/span>
    \n System<\/span>.<\/span>out.<\/span>println<\/span>(<\/span>res)<\/span>;<\/span>\/\/olleh<\/span>
    \n }<\/span>
    \n}<\/span><\/p>\n

    <\/h4>\n

    \u6ce8：\u4e09\u4e2a\u5bb9\u6613\u6df7\u7684\u70b9（\u7cbe\u70bc\u7248）
    \n\u2460 \u6253\u5370\u50cf\u5b57\u7b26\u4e32 \u2260 \u5b83\u5c31\u662f\u5b57\u7b26\u4e32<\/p>\n

    sb2 \u7684\u7c7b\u578b\u662f StringBuilder\u3002System.out.println \u4f1a\u81ea\u52a8\u8c03\u5b83\u7684 toString()，\u6240\u4ee5\u770b\u7740\u50cf\u6587\u5b57\u3002<\/p>\n

    \u2461 toString() \u5230\u5e95\u505a\u4e86\u4ec0\u4e48<\/p>\n

    \u6bd4\u55bb：StringBuilder \u662f\u80fd\u62c6\u80fd\u88c5\u7684\u6d3b\u5b57\u5370\u5237\u76d8（\u53ef append\u3001reverse），String \u662f\u6d47\u94f8\u5b9a\u578b\u7684\u94c5\u677f（\u5185\u5bb9\u4e0d\u53ef\u53d8）\u3002 String res = sb2.toString(); \u5c31\u662f\u628a\u5370\u5237\u76d8\u4e0a\u5f53\u524d\u7684\u5b57\u8a8a\u5199\u4e00\u4efd\u3001\u6253\u6210\u94c5\u677f\u2014\u2014\u662f\u590d\u5236，\u4e0d\u662f\u6362\u4e2a\u540d\u5b57\u3002<\/p>\n\n\u7c7b\u578b\u80fd\u505a\u4ec0\u4e48<\/tr>\n\n\n\n
    sb2（StringBuilder）<\/td>\nappend \/ reverse；\u4e0d\u80fd\u7528 substring()\u3001\u4e0d\u80fd\u7528 equals() \u6bd4\u5185\u5bb9<\/td>\n<\/tr>\n
    res（String）<\/td>\n\u6240\u6709 String \u65b9\u6cd5；\u5185\u5bb9\u4e0d\u53ef\u6539<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

    \u2462 \u8981\u6c42 String \u7684\u5730\u65b9\u4e0d\u80fd\u76f4\u63a5\u4f20 sb2<\/p>\n

    void<\/span> show<\/span>(<\/span>String<\/span> s)<\/span> {<\/span> }<\/span><\/p>\n

    show<\/span>(<\/span>sb2)<\/span>;<\/span> \/\/ \u274c \u7c7b\u578b\u4e0d\u5339\u914d<\/span>
    \nshow<\/span>(<\/span>sb2.<\/span>toString<\/span>(<\/span>)<\/span>)<\/span>;<\/span> \/\/ \u2705<\/span><\/p>\n

    \u4e00\u53e5\u8bdd：sb2 \u662f"\u80fd\u6539\u7684\u5bb9\u5668"，res \u662f"\u4e0d\u80fd\u6539\u7684\u6210\u54c1"，toString() \u8d1f\u8d23\u628a\u5bb9\u5668\u5185\u5bb9\u8a8a\u5199\u51fa\u6765\u505a\u6210\u6210\u54c1；\u7c7b\u578b\u4e0d\u540c，\u6253\u5370\u770b\u7740\u4e00\u6837 \u2260 \u662f\u540c\u4e00\u4e2a\u4e1c\u897f\u3002<\/p>\n

    📖\u4eca\u65e5\u77e5\u8bc6\u70b9 \u2014\u2014\u7ec3\u4e60\u9898：<\/h3>\n

    \u7ec3\u4e60\u98981：<\/h4>\n

    \u5b9a\u4e49\u4e00\u4e2a\u65b9\u6cd5，\u628a int \u6570\u7ec4\u4e2d\u7684\u6570\u636e\u6309\u7167\u6307\u5b9a\u7684\u683c\u5f0f\u62fc\u63a5\u6210\u4e00\u4e2a\u5b57\u7b26\u4e32\u8fd4\u56de，
    \n \u8c03\u7528\u8be5\u65b9\u6cd5，\u5e76\u5728\u63a7\u5236\u53f0\u8f93\u51fa\u7ed3\u679c\u3002
    \n \u4f8b\u5982：
    \n \u6570\u7ec4\u4e3a int[] arr = {1,2,3};
    \n \u6267\u884c\u65b9\u6cd5\u540e\u7684\u8f93\u51fa\u7ed3\u679c\u4e3a：[1, 2, 3]<\/p>\n

    \u7ec3\u4e60\u98982：<\/h4>\n

    \u952e\u76d8\u5f55\u5165\u5b57\u7b26\u4e32，\u5c06\u8be5\u5b57\u7b26\u4e32\u8fdb\u884c\u53cd\u8f6c，\u5f53\u8f93\u5165\u62dc\u62dc\u7684\u65f6\u5019\u7a0b\u5e8f\u505c\u6b62\u8fd0\u884c
    \n \u4f8b\u5982，\u952e\u76d8\u5f55\u5165 abc，\u8f93\u51fa\u7ed3\u679c cba<\/p>\n

    \u7ec3\u4e60\u98983：<\/h4>\n

    \u952e\u76d8\u5f55\u5165\u4efb\u610f\u5b57\u7b26\u4e32，\u8bf7\u6309\u957f\u5ea6\u4e3a8\u62c6\u5206\u6bcf\u4e2a\u8f93\u5165\u5b57\u7b26\u4e32\u5e76\u8fdb\u884c\u8f93\u51fa
    \n\u957f\u5ea6\u4e0d\u662f8\u6574\u6570\u500d\u7684\u5b57\u7b26\u4e32\u8bf7\u5728\u540e\u9762\u8865\u6570\u5b570，\u7a7a\u5b57\u7b26\u4e32\u4e0d\u5904\u7406\u3002
    \n\u4e3e\u4f8b：
    \n\u8f93\u5165：abcdabcda
    \n\u8f93\u51fa：
    \n\u7b2c\u4e00\u884c：abcdabcd
    \n\u7b2c\u4e8c\u884c：a0000000<\/p>\n

    \u7ec3\u4e60\u98984：<\/h4>\n

    \u5b9a\u4e49\u4e00\u4e2a\u4efb\u610f\u5b57\u7b26\u4e32，\u6253\u4e71\u91cc\u9762\u7684\u5185\u5bb9
    \n\u201cabcd\u201d—–>\u201cbcad\u201d<\/p>\n

    💻\u7ec3\u4e60\u4ee3\u7801<\/h3>\n

    \u7ec3\u4e60\u98981\u4ee3\u7801\u5b9e\u73b0：<\/h4>\n

    package<\/span> com.<\/span>itheima.<\/span>testdemo7<\/span>;<\/span><\/p>\n

    public<\/span> class<\/span> ArrayUtil<\/span> {<\/span>
    \n private<\/span> ArrayUtil<\/span>(<\/span>)<\/span>{<\/span><\/p>\n

    }<\/span>
    \n \/\/\u5b9a\u4e49\u65b9\u6cd5，\u628a\u6570\u7ec4\u53d8\u6210\u5b57\u7b26\u4e32\u8fdb\u884c\u8fd4\u56de<\/span>
    \n public<\/span> static<\/span> String<\/span> arrayToString1<\/span>(<\/span>int<\/span>[<\/span>]<\/span> arr)<\/span>{<\/span>
    \n String<\/span> str =<\/span> "["<\/span>;<\/span>
    \n \/\/\u904d\u5386\u6570\u7ec4<\/span>
    \n for<\/span> (<\/span>int<\/span> i =<\/span> 0<\/span>;<\/span> i <<\/span> arr.<\/span>length;<\/span> i++<\/span>)<\/span> {<\/span>
    \n if<\/span>(<\/span>i ==<\/span> arr.<\/span>length –<\/span> 1<\/span>)<\/span>{<\/span>
    \n str +=<\/span> arr[<\/span>i]<\/span> +<\/span> "]"<\/span>;<\/span>
    \n }<\/span>else<\/span>{<\/span>
    \n str +=<\/span> arr[<\/span>i]<\/span> +<\/span> ", "<\/span>;<\/span>
    \n }<\/span>
    \n }<\/span>
    \n return<\/span> str;<\/span>
    \n }<\/span>
    \n public<\/span> static<\/span> String<\/span> arrayToString2<\/span>(<\/span>int<\/span>[<\/span>]<\/span> arr)<\/span>{<\/span>
    \n StringBuilder<\/span> sb =<\/span> new<\/span> StringBuilder<\/span>(<\/span>"["<\/span>)<\/span>;<\/span>
    \n \/\/\u904d\u5386\u6570\u7ec4<\/span>
    \n for<\/span> (<\/span>int<\/span> i =<\/span> 0<\/span>;<\/span> i <<\/span> arr.<\/span>length;<\/span> i++<\/span>)<\/span> {<\/span>
    \n if<\/span>(<\/span>i ==<\/span> arr.<\/span>length –<\/span> 1<\/span>)<\/span>{<\/span>
    \n sb.<\/span>append<\/span>(<\/span>arr[<\/span>i]<\/span>)<\/span>.<\/span>append<\/span>(<\/span>"]"<\/span>)<\/span>;<\/span>
    \n }<\/span>else<\/span>{<\/span>
    \n sb.<\/span>append<\/span>(<\/span>arr[<\/span>i]<\/span>)<\/span>.<\/span>append<\/span>(<\/span>", "<\/span>)<\/span>;<\/span>
    \n }<\/span>
    \n }<\/span>
    \n return<\/span> sb.<\/span>toString<\/span>(<\/span>)<\/span>;<\/span>
    \n }<\/span>
    \n}<\/span><\/p>\n

    package<\/span> com.<\/span>itheima.<\/span>testdemo7<\/span>;<\/span><\/p>\n

    public<\/span> class<\/span> Test1<\/span> {<\/span>
    \n public<\/span> static<\/span> void<\/span> main<\/span>(<\/span>String<\/span>[<\/span>]<\/span> args)<\/span> {<\/span>
    \n \/*
    \n \u5b9a\u4e49\u4e00\u4e2a\u65b9\u6cd5，\u628a int \u6570\u7ec4\u4e2d\u7684\u6570\u636e\u6309\u7167\u6307\u5b9a\u7684\u683c\u5f0f\u62fc\u63a5\u6210\u4e00\u4e2a\u5b57\u7b26\u4e32\u8fd4\u56de，
    \n \u8c03\u7528\u8be5\u65b9\u6cd5，\u5e76\u5728\u63a7\u5236\u53f0\u8f93\u51fa\u7ed3\u679c\u3002
    \n \u4f8b\u5982：
    \n \u6570\u7ec4\u4e3a int[] arr = {1,2,3};
    \n \u6267\u884c\u65b9\u6cd5\u540e\u7684\u8f93\u51fa\u7ed3\u679c\u4e3a：[1, 2, 3]
    \n *\/<\/span>
    \n \/\/1\u3001\u5b9a\u4e49\u4e00\u4e2a\u6570\u7ec4<\/span>
    \n int<\/span>[<\/span>]<\/span> arr =<\/span> {<\/span>1<\/span>,<\/span> 2<\/span>,<\/span> 3<\/span>}<\/span>;<\/span>
    \n \/\/2\u3001\u8c03\u7528\u65b9\u6cd5\u5e76\u6253\u5370\u7ed3\u679c<\/span>
    \n String<\/span> res =<\/span> ArrayUtil<\/span>.<\/span>arrayToString2<\/span>(<\/span>arr)<\/span>;<\/span>
    \n System<\/span>.<\/span>out.<\/span>println<\/span>(<\/span>res)<\/span>;<\/span>
    \n }<\/span>
    \n}<\/span><\/p>\n

    \u7ec3\u4e60\u98982\u4ee3\u7801\u5b9e\u73b0：<\/h4>\n

    package<\/span> com.<\/span>itheima.<\/span>testdemo7<\/span>;<\/span><\/p>\n

    import<\/span> java.<\/span>util.<\/span><\/span>Scanner<\/span><\/span>;<\/span><\/p>\n

    public<\/span> class<\/span> Test2<\/span> {<\/span>
    \n public<\/span> static<\/span> void<\/span> main<\/span>(<\/span>String<\/span>[<\/span>]<\/span> args)<\/span> {<\/span>
    \n \/*
    \n \u952e\u76d8\u5f55\u5165\u5b57\u7b26\u4e32，\u5c06\u8be5\u5b57\u7b26\u4e32\u8fdb\u884c\u53cd\u8f6c，\u5f53\u8f93\u5165\u62dc\u62dc\u7684\u65f6\u5019\u7a0b\u5e8f\u505c\u6b62\u8fd0\u884c
    \n \u4f8b\u5982，\u952e\u76d8\u5f55\u5165 abc，\u8f93\u51fa\u7ed3\u679c cba
    \n for:\u77e5\u9053\u5faa\u73af\u6b21\u6570
    \n while:\u77e5\u9053\u5faa\u73af\u7ed3\u675f\u6761\u4ef6，\u4e0d\u77e5\u9053\u5faa\u73af\u6b21\u6570
    \n *\/<\/span>
    \n while<\/span>(<\/span>true<\/span>)<\/span>{<\/span>
    \n \/\/1.\u952e\u76d8\u5f55\u5165\u5b57\u7b26\u4e32<\/span>
    \n Scanner<\/span> sc =<\/span> new<\/span> Scanner<\/span>(<\/span>System<\/span>.<\/span>in)<\/span>;<\/span>
    \n System<\/span>.<\/span>out.<\/span>println<\/span>(<\/span>"\u8bf7\u8f93\u5165\u4e00\u4e2a\u5b57\u7b26\u4e32："<\/span>)<\/span>;<\/span>
    \n String<\/span> str =<\/span> sc.<\/span>next<\/span>(<\/span>)<\/span>;<\/span>
    \n \/\/2.\u5224\u65ad\u5b57\u7b26\u4e32\u662f\u5426\u4e3a\u62dc\u62dc<\/span>
    \n if<\/span>(<\/span>str.<\/span>equals<\/span>(<\/span>"\u62dc\u62dc"<\/span>)<\/span>)<\/span>{<\/span>
    \n System<\/span>.<\/span>out.<\/span>println<\/span>(<\/span>"\u7a0b\u5e8f\u505c\u6b62\u8fd0\u884c"<\/span>)<\/span>;<\/span>
    \n break<\/span>;<\/span>
    \n }<\/span>else<\/span>{<\/span>
    \n StringBuilder<\/span> sb =<\/span> new<\/span> StringBuilder<\/span>(<\/span>str)<\/span>;<\/span>
    \n sb.<\/span>reverse<\/span>(<\/span>)<\/span>;<\/span>
    \n String<\/span> res =<\/span> sb.<\/span>toString<\/span>(<\/span>)<\/span>;<\/span>
    \n System<\/span>.<\/span>out.<\/span>println<\/span>(<\/span>res)<\/span>;<\/span>
    \n }<\/span>
    \n }<\/span>
    \n }<\/span>
    \n }<\/span><\/p>\n

    \u7ec3\u4e60\u98983\u4ee3\u7801\u5b9e\u73b0：<\/h4>\n

    package<\/span> com.<\/span>itheima.<\/span>testdemo7<\/span>;<\/span><\/p>\n

    import<\/span> java.<\/span>util.<\/span><\/span>Scanner<\/span><\/span>;<\/span><\/p>\n

    public<\/span> class<\/span> Test3Case2<\/span> {<\/span>
    \n public<\/span> static<\/span> void<\/span> main<\/span>(<\/span>String<\/span>[<\/span>]<\/span> args)<\/span> {<\/span>
    \n \/*
    \n \u952e\u76d8\u5f55\u5165\u4efb\u610f\u5b57\u7b26\u4e32，\u8bf7\u6309\u957f\u5ea6\u4e3a8\u62c6\u5206\u6bcf\u4e2a\u8f93\u5165\u5b57\u7b26\u4e32\u5e76\u8fdb\u884c\u8f93\u51fa
    \n \u957f\u5ea6\u4e0d\u662f8\u6574\u6570\u500d\u7684\u5b57\u7b26\u4e32\u8bf7\u5728\u540e\u9762\u8865\u6570\u5b570，\u7a7a\u5b57\u7b26\u4e32\u4e0d\u5904\u7406\u3002
    \n \u4e3e\u4f8b：
    \n \u8f93\u5165：abcdabcda
    \n \u8f93\u51fa：
    \n \u7b2c\u4e00\u884c：abcdabcd
    \n \u7b2c\u4e8c\u884c：a0000000
    \n *\/<\/span>
    \n \/\/ 1. \u952e\u76d8\u5f55\u5165\u4efb\u610f\u5b57\u7b26\u4e32<\/span>
    \n Scanner<\/span> sc =<\/span> new<\/span> Scanner<\/span>(<\/span>System<\/span>.<\/span>in)<\/span>;<\/span>
    \n System<\/span>.<\/span>out.<\/span>println<\/span>(<\/span>"\u8bf7\u8f93\u5165\u4e00\u4e2a\u5b57\u7b26\u4e32："<\/span>)<\/span>;<\/span>
    \n String<\/span> str =<\/span> sc.<\/span>next<\/span>(<\/span>)<\/span>;<\/span>
    \n \/\/2.\u76f4\u63a5\u5728str\u7684\u540e\u9762\u88650<\/span>
    \n \/\/abcdabcda0000000<\/span>
    \n \/\/\u8ba1\u7b97\u6700\u540e\u4e00\u884c\u6709\u591a\u5c11\u4e2a\u5b57\u7b26<\/span>
    \n int<\/span> lastLineCount =<\/span> str.<\/span>length<\/span>(<\/span>)<\/span> %<\/span> 8<\/span>;<\/span>
    \n \/\/\u8ba1\u7b97\u6700\u540e\u4e00\u884c\u88650\u7684\u4e2a\u6570<\/span>
    \n int<\/span> count =<\/span> 8<\/span> –<\/span> lastLineCount;<\/span>
    \n if<\/span>(<\/span>lastLineCount !=<\/span> 0<\/span>)<\/span>{<\/span>
    \n \/\/\u83b7\u53d6\u6700\u540e\u4e00\u884c\u8865\u76840<\/span>
    \n String<\/span> s =<\/span> "0000000"<\/span>.<\/span>substring<\/span>(<\/span>0<\/span>,<\/span> count)<\/span>;<\/span>
    \n \/\/\u62fc\u63a5<\/span>
    \n str =<\/span> str +<\/span> s;<\/span>
    \n }<\/span>
    \n \/\/System.out.println(str);<\/span>
    \n \/\/3.\u6bcf8\u4e2a\u6253\u5370\u4e00\u884c<\/span>
    \n \/\/i += 8,\u8868\u793a\u6bcf\u6b21\u622a\u53d68\u4e2a<\/span>
    \n \/\/ \u7b2c\u4e00\u884c：\u4ece0\u7d22\u5f15\u5f00\u59cb<\/span>
    \n \/\/ \u7b2c\u4e8c\u884c：\u4ece8\u7d22\u5f15\u5f00\u59cb<\/span>
    \n \/\/\u622a\u53d6：substring<\/span>
    \n for<\/span>(<\/span>int<\/span> i =<\/span> 0<\/span>;<\/span> i <<\/span> str.<\/span>length<\/span>(<\/span>)<\/span>;<\/span> i +=<\/span> 8<\/span>)<\/span>{<\/span>
    \n String<\/span> res =<\/span> str.<\/span>substring<\/span>(<\/span>i,<\/span> i +<\/span> 8<\/span>)<\/span>;<\/span>
    \n System<\/span>.<\/span>out.<\/span>println<\/span>(<\/span>res)<\/span>;<\/span>
    \n }<\/span><\/p>\n

    }<\/span>
    \n}<\/span><\/p>\n

    \u7ec3\u4e60\u98984\u4ee3\u7801\u5b9e\u73b0：<\/h4>\n

    package<\/span> com.<\/span>itheima.<\/span>testdemo7<\/span>;<\/span><\/p>\n

    import<\/span> java.<\/span>util.<\/span><\/span>Random<\/span><\/span>;<\/span><\/p>\n

    public<\/span> class<\/span> Test5<\/span> {<\/span>
    \n public<\/span> static<\/span> void<\/span> main<\/span>(<\/span>String<\/span>[<\/span>]<\/span> args)<\/span> {<\/span>
    \n \/\/ \u5b9a\u4e49\u4e00\u4e2a\u4efb\u610f\u5b57\u7b26\u4e32，\u6253\u4e71\u91cc\u9762\u7684\u5185\u5bb9<\/span>
    \n \/\/ \u201cabcd\u201d—–>\u201cbcad\u201d<\/span><\/p>\n

    \/\/\u5b9a\u4e49\u4e00\u4e2a\u5b57\u7b26\u4e32<\/span>
    \n String<\/span> str =<\/span> "abcd"<\/span>;<\/span>
    \n \/\/\u628a\u5b57\u7b26\u4e32\u8f6c\u6362\u6210\u5b57\u7b26\u6570\u7ec4<\/span>
    \n char<\/span>[<\/span>]<\/span> arr =<\/span> str.<\/span>toCharArray<\/span>(<\/span>)<\/span>;<\/span>
    \n \/\/\u6253\u4e71\u5b57\u7b26\u6570\u7ec4arr\u4e2d\u7684\u5185\u5bb9<\/span>
    \n Random<\/span> r =<\/span> new<\/span> Random<\/span>(<\/span>)<\/span>;<\/span>
    \n for<\/span> (<\/span>int<\/span> i =<\/span> 0<\/span>;<\/span> i <<\/span> arr.<\/span>length;<\/span> i++<\/span>)<\/span> {<\/span>
    \n \/\/\u83b7\u53d6\u4e00\u4e2a\u968f\u673a\u7d22\u5f15<\/span>
    \n int<\/span> randomIndex =<\/span> r.<\/span>nextInt<\/span>(<\/span>arr.<\/span>length)<\/span>;<\/span>
    \n \/\/\u4f9d\u6b21\u5f97\u5230\u6570\u7ec4\u7684\u6bcf\u4e00\u4e2a\u5b57\u7b26<\/span>
    \n char<\/span> temp =<\/span> arr[<\/span>i]<\/span>;<\/span>
    \n arr[<\/span>i]<\/span> =<\/span> arr[<\/span>randomIndex]<\/span>;<\/span>
    \n arr[<\/span>randomIndex]<\/span> =<\/span> temp;<\/span>
    \n }<\/span>
    \n \/\/\u628a\u5b57\u7b26\u6570\u7ec4\u8f6c\u6362\u6210\u5b57\u7b26\u4e32<\/span>
    \n String<\/span> result =<\/span> new<\/span> String<\/span>(<\/span>arr)<\/span>;<\/span>
    \n \/\/\u8f93\u51fa\u7ed3\u679c<\/span>
    \n System<\/span>.<\/span>out.<\/span>println<\/span>(<\/span>result)<\/span>;<\/span>
    \n }<\/span>
    \n}<\/span><\/p>\n

    5.\u7b97\u6cd5\u7ec3\u4e60——\u5b57\u7b26\u4e32\u8ba1\u7b97：<\/p>\n

    package<\/span> com.<\/span>itheima.<\/span>testdemo7<\/span>;<\/span><\/p>\n

    public<\/span> class<\/span> Test6<\/span> {<\/span>
    \n public<\/span> static<\/span> void<\/span> main<\/span>(<\/span>String<\/span>[<\/span>]<\/span> args)<\/span> {<\/span>
    \n \/*
    \n \u5b57\u7b26\u4e32\u8ba1\u7b97
    \n \u5b9a\u4e49\u4e24\u4e2a\u5b57\u7b26\u4e32，\u8bb0\u5f55\u4e3a\u975e\u8d1f\u6574\u6570，\u6c42\u5b83\u4eec\u7684\u548c\u3002
    \n \u8f93\u5165："12395" \u548c "133"，\u8f93\u51fa："12528"
    \n \u6ce8\u610f：\u9700\u8981\u6570\u636e\u8fc7\u5927，\u8d85\u51faint\u53d6\u503c\u8303\u56f4\u7684\u60c5\u51b5
    \n *\/<\/span>
    \n \/\/1.\u5b9a\u4e49\u4e24\u4e2a\u5b57\u7b26\u4e32<\/span>
    \n String<\/span> str1 =<\/span> "12395"<\/span>;<\/span>
    \n String<\/span> str2 =<\/span> "133"<\/span>;<\/span>
    \n \/\/2.\u628a\u4e24\u4e2a\u5b57\u7b26\u4e32\u7684\u6570\u636e\u653e\u5165int\u7c7b\u578b\u7684\u6570\u7ec4\u91cc\u9762<\/span>
    \n int<\/span> len =<\/span> str1.<\/span>length<\/span>(<\/span>)<\/span> >=<\/span> str2.<\/span>length<\/span>(<\/span>)<\/span> ?<\/span> str1.<\/span>length<\/span>(<\/span>)<\/span> :<\/span> str2.<\/span>length<\/span>(<\/span>)<\/span>;<\/span>
    \n int<\/span>[<\/span>]<\/span> arr1 =<\/span> copyData<\/span>(<\/span>str1,<\/span> len)<\/span>;<\/span>
    \n int<\/span>[<\/span>]<\/span> arr2 =<\/span> copyData<\/span>(<\/span>str2,<\/span> len)<\/span>;<\/span>
    \n \/\/3.\u5b9a\u4e49\u4e00\u4e2a\u6570\u7ec4\u5b58\u5165\u6700\u7ec8\u7ed3\u679c，\u6570\u7ec4\u957f\u5ea6+1<\/span>
    \n int<\/span>[<\/span>]<\/span> sum =<\/span> new<\/span> int<\/span>[<\/span>len +<\/span> 1<\/span>]<\/span>;<\/span>
    \n \/\/4.\u5b9a\u4e49\u4e00\u4e2a\u53d8\u91cf\u8868\u793a\u8fdb\u4f4d<\/span>
    \n int<\/span> num =<\/span> 0<\/span>;<\/span>
    \n \/\/5.\u6838\u5fc3：\u904d\u5386\u6570\u7ec4：\u4ece\u4e2a\u4f4d（\u6700\u5927\u7d22\u5f15）\u4f4d\u7f6e\u5f00\u59cb\u904d\u5386<\/span>
    \n \/\/arr[i] + arr2[i] + num = \u7ed3\u679c<\/span>
    \n \/\/\u7ed3\u679c\u7684\u4e2a\u4f4d — sum\u6570\u7ec4\u5f53\u4e2d<\/span>
    \n \/\/\u7ed3\u679c\u7684\u5341\u4f4d — \u8fdb\u4f4dnum<\/span>
    \n for<\/span> (<\/span>int<\/span> i =<\/span> arr1.<\/span>length –<\/span> 1<\/span>;<\/span> i >=<\/span> 0<\/span>;<\/span> i—<\/span>)<\/span> {<\/span>
    \n int<\/span> temp =<\/span> arr1[<\/span>i]<\/span> +<\/span> arr2[<\/span>i]<\/span> +<\/span> num;<\/span>
    \n sum[<\/span>i +<\/span> 1<\/span>]<\/span> =<\/span> temp %<\/span> 10<\/span>;<\/span>
    \n num =<\/span> temp \/<\/span> 10<\/span>;<\/span>
    \n }<\/span>
    \n \/\/6.\u8003\u8651\u9996\u4f4d<\/span>
    \n sum[<\/span>0<\/span>]<\/span> =<\/span> num;<\/span>
    \n \/\/7.\u628a\u6570\u7ec4\u5f53\u4e2d\u7684\u6570\u636e，\u8fde\u63a5\u6210\u4e00\u4e2a\u5b57\u7b26\u4e32<\/span>
    \n StringBuilder<\/span> sb =<\/span> new<\/span> StringBuilder<\/span>(<\/span>)<\/span>;<\/span>
    \n if<\/span>(<\/span>sum[<\/span>0<\/span>]<\/span> !=<\/span> 0<\/span>)<\/span>{<\/span>
    \n sb.<\/span>append<\/span>(<\/span>sum[<\/span>0<\/span>]<\/span>)<\/span>;<\/span>
    \n }<\/span>
    \n for<\/span> (<\/span>int<\/span> i =<\/span> 1<\/span>;<\/span> i <<\/span> sum.<\/span>length;<\/span> i++<\/span>)<\/span> {<\/span>
    \n sb.<\/span>append<\/span>(<\/span>sum[<\/span>i]<\/span>)<\/span>;<\/span>
    \n }<\/span>
    \n System<\/span>.<\/span>out.<\/span>println<\/span>(<\/span>sb.<\/span>toString<\/span>(<\/span>)<\/span>)<\/span>;<\/span><\/p>\n

    }<\/span><\/p>\n

    public<\/span> static<\/span> int<\/span>[<\/span>]<\/span> copyData<\/span>(<\/span>String<\/span> str,<\/span> int<\/span> len)<\/span> {<\/span>
    \n \/\/\u5b9a\u4e49int\u7c7b\u578b\u6570\u7ec4<\/span>
    \n int<\/span>[<\/span>]<\/span> arr =<\/span> new<\/span> int<\/span>[<\/span>len]<\/span>;<\/span>
    \n \/\/\u628a\u5b57\u7b26\u4e32\u7684\u6570\u636e，\u653e\u5165\u5230\u6570\u7ec4\u5f53\u4e2d<\/span>
    \n \/\/\u5b9a\u4e49\u4e00\u4e2a\u53d8\u91cf\u8868\u793a\u6570\u7ec4\u4e2d\u5e94\u5b58\u5165\u7684\u4f4d\u7f6e<\/span>
    \n int<\/span> index =<\/span> arr.<\/span>length –<\/span> 1<\/span>;<\/span>
    \n for<\/span> (<\/span>int<\/span> i =<\/span> str.<\/span>length<\/span>(<\/span>)<\/span> –<\/span> 1<\/span>;<\/span> i >=<\/span> 0<\/span>;<\/span> i—<\/span>)<\/span> {<\/span>
    \n char<\/span> c =<\/span> str.<\/span>charAt<\/span>(<\/span>i)<\/span>;<\/span>\/\/\u83b7\u53d6\u5355\u4e2a\u5b57\u7b26<\/span>
    \n arr[<\/span>index]<\/span> =<\/span> c –<\/span> 48<\/span>;<\/span>\/\/\u5b57\u7b26\u8f6c\u4e3a\u6570\u5b57<\/span>
    \n index—<\/span>;<\/span>\/\/\u6570\u7ec4\u4e2d\u5e94\u5b58\u5165\u7684\u4f4d\u7f6e\u51cf1<\/span>
    \n }<\/span>
    \n return<\/span> arr;<\/span><\/p>\n

    }<\/span><\/p>\n

    }<\/span><\/p>\n

    package<\/span> com.<\/span>itheima.<\/span>testdemo7<\/span>;<\/span><\/p>\n

    public<\/span> class<\/span> Test7<\/span> {<\/span>
    \n public<\/span> static<\/span> void<\/span> main<\/span>(<\/span>String<\/span>[<\/span>]<\/span> args)<\/span>{<\/span>
    \n \/\/'1' —1 49<\/span>
    \n \/\/'2' —2 50<\/span>
    \n \/\/'3' —3 51<\/span>
    \n \/\/'4' —4 52<\/span>
    \n \/\/'5' —5 53<\/span>
    \n \/\/'6' —6 54<\/span>
    \n \/\/'7' —7 55<\/span>
    \n \/\/'8' —8 56<\/span>
    \n \/\/'9' —9 57<\/span>
    \n \/\/'0' —0 48<\/span>
    \n char<\/span> c =<\/span> '9'<\/span>;<\/span>
    \n System<\/span>.<\/span>out.<\/span>println<\/span>(<\/span>c –<\/span> 48<\/span>)<\/span>;<\/span>\/\/9<\/span>
    \n }<\/span>
    \n}<\/span><\/p>\n

    📖\u4eca\u65e5\u77e5\u8bc6\u70b9 \u2014\u2014\u5b57\u7b26\u4e32\u4f5c\u4e1a<\/h3>\n

    \u4f5c\u4e1a1：<\/h5>\n

    💻\u7ec3\u4e60\u4ee3\u7801<\/h3>\n

    package<\/span> com.<\/span>itheima.<\/span>testdemo7<\/span>;<\/span><\/p>\n

    public<\/span> class<\/span> Test8<\/span> {<\/span>
    \n public<\/span> static<\/span> void<\/span> main<\/span>(<\/span>String<\/span>[<\/span>]<\/span> args)<\/span> {<\/span>
    \n \/*
    \n \u6570\u636e\u8131\u654f（\u4f5c\u4e1a1）
    \n1\u3001\u628a\u4efb\u610f\u624b\u673a\u53f7\u4e2d\u95f4\u56db\u4f4d\u53d8\u6210****
    \n2\u3001\u4fdd\u7559\u90ae\u7bb1\u540d\u7b2c\u4e00\u4e2a\u5b57\u6bcd，\u4fdd\u7559@\u540e\u9762\u7684\u5185\u5bb9
    \n131 1234 5678 -> 131****5678
    \nzw1234@163.com -> z*@163.com
    \n *\/<\/span>
    \n String<\/span> phoneNumber =<\/span> "13112345678"<\/span>;<\/span>
    \n \/\/substring\u622a\u53d6\u5b57\u7b26\u4e32<\/span>
    \n \/\/\u524d3\u4f4d<\/span>
    \n String<\/span> phonePrefix =<\/span> phoneNumber.<\/span>substring<\/span>(<\/span>0<\/span>,<\/span>3<\/span>)<\/span>;<\/span>
    \n \/\/\u540e4\u4f4d<\/span>
    \n String<\/span> phoneSuffix =<\/span> phoneNumber.<\/span>substring<\/span>(<\/span>7<\/span>)<\/span>;<\/span>
    \n System<\/span>.<\/span>out.<\/span>println<\/span>(<\/span>phonePrefix +<\/span> "****"<\/span> +<\/span> phoneSuffix)<\/span>;<\/span><\/p>\n

    String<\/span> email =<\/span> "zw1234765489@163.com"<\/span>;<\/span>
    \n \/\/\u4fdd\u7559\u90ae\u7bb1\u540d\u7b2c\u4e00\u4e2a\u5b57\u6bcd<\/span>
    \n String<\/span> emailPrefix =<\/span> email.<\/span>substring<\/span>(<\/span>0<\/span>,<\/span>1<\/span>)<\/span>;<\/span>
    \n \/\/\u4fdd\u7559@\u540e\u9762\u7684\u5185\u5bb9<\/span>
    \n String<\/span> emailSuffix =<\/span> email.<\/span>substring<\/span>(<\/span>email.<\/span>indexOf<\/span>(<\/span>"@"<\/span>)<\/span>)<\/span>;<\/span>
    \n System<\/span>.<\/span>out.<\/span>println<\/span>(<\/span>emailPrefix +<\/span> "*"<\/span> +<\/span> emailSuffix)<\/span>;<\/span>
    \n }<\/span>
    \n}<\/span><\/p>\n

    \u4f5c\u4e1a2：<\/h5>\n

    package<\/span> com.<\/span>itheima.<\/span>testdemo7<\/span>;<\/span><\/p>\n

    import<\/span> java.<\/span>util.<\/span><\/span>Scanner<\/span><\/span>;<\/span><\/p>\n

    public<\/span> class<\/span> Test9<\/span> {<\/span>
    \n public<\/span> static<\/span> void<\/span> main<\/span>(<\/span>String<\/span>[<\/span>]<\/span> args)<\/span> {<\/span>
    \n \/*
    \n \u8ba1\u7b97\u67d0\u4e2a\u5b57\u7b26\u51fa\u73b0\u7684\u6b21\u6570（\u4f5c\u4e1a2）
    \n \u63cf\u8ff0
    \n \u5199\u51fa\u4e00\u4e2a\u7a0b\u5e8f，\u63a5\u53d7\u4e00\u4e2a\u7531\u5b57\u6bcd\u3001\u6570\u5b57\u548c\u7a7a\u683c\u7ec4\u6210\u7684\u5b57\u7b26\u4e32，\u548c\u4e00\u4e2a\u5b57\u7b26，\u7136\u540e\u8f93\u51fa\u8f93\u5165\u5b57\u7b26\u4e32\u4e2d\u8be5\u5b57\u7b26\u7684\u51fa\u73b0\u6b21\u6570\u3002（\u4e0d\u533a\u5206\u5927\u5c0f\u5199\u5b57\u6bcd）
    \n \u6570\u636e\u8303\u56f4：1 \u2264 n \u2264 1000
    \n \u8f93\u5165\u63cf\u8ff0：
    \n \u7b2c\u4e00\u884c\u8f93\u5165\u4e00\u4e2a\u7531\u5b57\u6bcd\u3001\u6570\u5b57\u548c\u7a7a\u683c\u7ec4\u6210\u7684\u5b57\u7b26\u4e32，\u7b2c\u4e8c\u884c\u8f93\u5165\u4e00\u4e2a\u5b57\u7b26（\u4fdd\u8bc1\u8be5\u5b57\u7b26\u4e0d\u4e3a\u7a7a\u683c）\u3002
    \n \u8f93\u51fa\u63cf\u8ff0：
    \n \u8f93\u51fa\u8f93\u5165\u5b57\u7b26\u4e32\u4e2d\u542b\u6709\u8be5\u5b57\u7b26\u7684\u4e2a\u6570\u3002（\u4e0d\u533a\u5206\u5927\u5c0f\u5199\u5b57\u6bcd）
    \n \u793a\u4f8b1
    \n \u8f93\u5165：
    \n ABCabc
    \n A
    \n \u8f93\u51fa：
    \n 2
    \n *\/<\/span>
    \n \/\/1.\u952e\u76d8\u5f55\u5165\u4e00\u4e2a\u5b57\u7b26<\/span>
    \n Scanner<\/span> sc =<\/span> new<\/span> Scanner<\/span>(<\/span>System<\/span>.<\/span>in)<\/span>;<\/span>
    \n System<\/span>.<\/span>out.<\/span>println<\/span>(<\/span>"\u8bf7\u8f93\u5165\u4e00\u4e2a\u5b57\u7b26\u4e32："<\/span>)<\/span>;<\/span>
    \n String<\/span> str =<\/span> sc.<\/span>nextLine<\/span>(<\/span>)<\/span>;<\/span>
    \n \/\/2.\u76ee\u6807\u5b57\u7b26<\/span>
    \n char<\/span> target =<\/span> sc.<\/span>next<\/span>(<\/span>)<\/span>.<\/span>charAt<\/span>(<\/span>0<\/span>)<\/span>;<\/span>
    \n \/\/\u7edf\u8ba1\u76ee\u6807\u5b57\u7b26\u51fa\u73b0\u7684\u6b21\u6570<\/span>
    \n int<\/span> count =<\/span> 0<\/span>;<\/span>
    \n \/\/\u5c06\u76ee\u6807\u5b57\u7b26\u8f6c\u6362\u6210\u5c0f\u5199<\/span>
    \n char<\/span> t =<\/span> Character<\/span>.<\/span>toLowerCase<\/span>(<\/span>target)<\/span>;<\/span>
    \n \/\/3.\u904d\u5386\u5b57\u7b26\u4e32，\u83b7\u53d6\u6bcf\u4e00\u4e2a\u5b57\u7b26\u5e76\u548c\u76ee\u6807\u5b57\u7b26\u8fdb\u884c\u6bd4\u8f83<\/span>
    \n for<\/span> (<\/span>int<\/span> i =<\/span> 0<\/span>;<\/span> i <<\/span> str.<\/span>length<\/span>(<\/span>)<\/span>;<\/span> i++<\/span>)<\/span>{<\/span>
    \n char<\/span> c =<\/span> str.<\/span>charAt<\/span>(<\/span>i)<\/span>;<\/span>
    \n \/\/\u5f53\u524d\u5b57\u7b26\u548c\u76ee\u6807\u5b57\u7b26\u90fd\u8f6c\u4e3a\u5c0f\u5199<\/span>
    \n if<\/span>(<\/span>Character<\/span>.<\/span>toLowerCase<\/span>(<\/span>c)<\/span> ==<\/span> t)<\/span>{<\/span>
    \n count++<\/span>;<\/span>
    \n }<\/span>
    \n }<\/span>
    \n System<\/span>.<\/span>out.<\/span>println<\/span>(<\/span>count)<\/span>;<\/span>
    \n }<\/span>
    \n}<\/span><\/p>\n

    \u4f5c\u4e1a3：<\/h5>\n

    package<\/span> com.<\/span>itheima.<\/span>testdemo7<\/span>;<\/span><\/p>\n

    public<\/span> class<\/span> Test11<\/span> {<\/span>
    \n public<\/span> static<\/span> void<\/span> main<\/span>(<\/span>String<\/span>[<\/span>]<\/span> args)<\/span> {<\/span>
    \n \/*
    \n \u3010\u6848\u4f8b\u3011 \u5b57\u7b26\u4e32\u8f6c\u6362（\u4f5c\u4e1a3）
    \n \u7ed9\u4f60\u4e00\u4e2a\u5b57\u7b26\u4e32 s，\u7531\u82e5\u5e72\u5355\u8bcd\u7ec4\u6210，\u5355\u8bcd\u524d\u540e\u7528\u4e00\u4e9b\u7a7a\u683c\u5b57\u7b26\u9694\u5f00\u3002\u8fd4\u56de\u5b57\u7b26\u4e32\u4e2d \u6700\u540e\u4e00\u4e2a \u5355\u8bcd\u7684\u957f\u5ea6\u3002
    \n \u5355\u8bcd \u662f\u6307\u4ec5\u7531\u5b57\u6bcd\u7ec4\u6210\u3001\u4e0d\u5305\u542b\u4efb\u4f55\u7a7a\u683c\u5b57\u7b26\u7684\u6700\u5927\u5b50\u5b57\u7b26\u4e32\u3002
    \n \u793a\u4f8b 1：
    \n \u8f93\u5165：s = "Hello World"
    \n \u8f93\u51fa：5
    \n \u89e3\u91ca：\u6700\u540e\u4e00\u4e2a\u5355\u8bcd\u662f\u201cWorld\u201d，\u957f\u5ea6\u4e3a 5\u3002<\/p>\n

    \u793a\u4f8b 2：
    \n \u8f93\u5165：s = " fly me to the moon "
    \n \u8f93\u51fa：4
    \n \u89e3\u91ca：\u6700\u540e\u4e00\u4e2a\u5355\u8bcd\u662f\u201cmoon\u201d，\u957f\u5ea6\u4e3a 4\u3002 (\u6ce8：\u539f\u56fe\u4e2d\u201cmoon\u201d\u4e0b\u65b9\u6709\u7ea2\u8272\u4e0b\u5212\u7ebf)<\/p>\n

    \u793a\u4f8b 3：
    \n \u8f93\u5165：s = "luffy is still joyboy"
    \n \u8f93\u51fa：6
    \n \u89e3\u91ca：\u6700\u540e\u4e00\u4e2a\u5355\u8bcd\u662f\u957f\u5ea6\u4e3a 6 \u7684\u201cjoyboy\u201d\u3002<\/p>\n

    \u601d\u8def：\u4ece\u6700\u540e\u4e00\u4e2a\u5355\u8bcd\u51fa\u53d1，\u5411\u5de6\u904d\u5386，\u76f4\u5230\u9047\u5230\u7a7a\u683c\u4e3a\u6b62，\u5373\u53ef\u5f97\u5230\u6700\u540e\u4e00\u4e2a\u5355\u8bcd\u7684\u957f\u5ea6\u3002
    \n *\/<\/span>
    \n \/\/1.\u5b9a\u4e49\u4e00\u4e2a\u5b57\u7b26\u4e32<\/span>
    \n String<\/span> s =<\/span> "Hello World"<\/span>;<\/span><\/p>\n

    int<\/span> len =<\/span> 0<\/span>;<\/span>
    \n for<\/span>(<\/span>int<\/span> i =<\/span> s.<\/span>length<\/span>(<\/span>)<\/span> –<\/span> 1<\/span>;<\/span>i >=<\/span> 0<\/span>;<\/span>i—<\/span>)<\/span>{<\/span>
    \n if<\/span>(<\/span>s.<\/span>charAt<\/span>(<\/span>i)<\/span> ==<\/span> ' '<\/span>)<\/span>{<\/span>
    \n break<\/span>;<\/span>
    \n }<\/span>else<\/span>{<\/span>
    \n len++<\/span>;<\/span>
    \n }<\/span>
    \n }<\/span>
    \n System<\/span>.<\/span>out.<\/span>println<\/span>(<\/span>len)<\/span>;<\/span>
    \n }<\/span>
    \n}<\/span><\/p>\n

    \u4f5c\u4e1a4：<\/h5>\n

    package<\/span> com.<\/span>itheima.<\/span>testdemo7<\/span>;<\/span><\/p>\n

    public<\/span> class<\/span> Test10<\/span> {<\/span>
    \n public<\/span> static<\/span> void<\/span> main<\/span>(<\/span>String<\/span>[<\/span>]<\/span> args)<\/span> {<\/span>
    \n \/*
    \n \u3010\u6848\u4f8b\u3011\u5b57\u7b26\u4e32\u83b7\u53d6\u4fe1\u606f（\u4f5c\u4e1a4）
    \n \u6211\u4eec\u7684\u8eab\u4efd\u8bc1\u53f7\u7801\u62e5\u6709\u4e00\u5b9a\u7684\u89c4\u5219：
    \n 1\u30012\u4f4d：\u7701\u4efd\u3000\u3000\u3000\u3000\u3000\u30003\u30014\u4f4d：\u57ce\u5e02
    \n 5\u30016\u4f4d：\u533a\u53bf\u3000\u3000\u3000\u3000\u3000\u30007-14\u4f4d：\u51fa\u751f\u5e74\u3001\u6708\u3001\u65e5
    \n 15\u300116\u4f4d：\u6240\u5728\u5730\u6d3e\u51fa\u6240\u300017\u4f4d：\u6027\u522b（\u5947\u6570\u7537\u6027，\u5076\u6570\u5973\u6027）
    \n 18\u4f4d：\u4e2a\u4eba\u4fe1\u606f\u7801（\u968f\u673a\u4ea7\u751f）<\/p>\n

    \u8981\u6c42：
    \n \u5047\u8bbe\u6709\u8eab\u4efd\u8bc1：321104200801121234，\u83b7\u53d6\u4eba\u7269\u7684\u51fa\u751f\u5e74\u6708\u65e5\u548c\u6027\u522b\u8fdb\u884c\u8f93\u51fa\u3002<\/p>\n

    \u8f93\u51fa\u7ed3\u679c：
    \n \u51fa\u751f\u5e74\u6708\u65e5：2008\u5e7401\u670812\u65e5
    \n \u6027\u522b\u4e3a：\u7537
    \n *\/<\/span>
    \n String<\/span> id =<\/span> "321104200801121234"<\/span>;<\/span>
    \n String<\/span> year =<\/span> id.<\/span>substring<\/span>(<\/span>6<\/span>,<\/span>10<\/span>)<\/span>;<\/span>
    \n String<\/span> month =<\/span> id.<\/span>substring<\/span>(<\/span>10<\/span>,<\/span>12<\/span>)<\/span>;<\/span>
    \n String<\/span> day =<\/span> id.<\/span>substring<\/span>(<\/span>12<\/span>,<\/span>14<\/span>)<\/span>;<\/span>
    \n char<\/span> genderChar =<\/span> id.<\/span>charAt<\/span>(<\/span>16<\/span>)<\/span>;<\/span>\/\/\u83b7\u53d6\u6027\u522b\u5b57\u7b26<\/span>
    \n int<\/span> genderNum =<\/span> genderChar –<\/span> '0'<\/span>;<\/span>
    \n System<\/span>.<\/span>out.<\/span>println<\/span>(<\/span>"\u51fa\u751f\u5e74\u6708\u65e5："<\/span> +<\/span> year +<\/span> "\u5e74"<\/span> +<\/span> month +<\/span> "\u6708"<\/span> +<\/span> day +<\/span> "\u65e5"<\/span>)<\/span>;<\/span>
    \n if<\/span> (<\/span>genderNum %<\/span> 2<\/span> ==<\/span> 0<\/span>)<\/span> {<\/span>
    \n System<\/span>.<\/span>out.<\/span>println<\/span>(<\/span>"\u6027\u522b\u4e3a：\u5973"<\/span>)<\/span>;<\/span>
    \n }<\/span> else<\/span> {<\/span>
    \n System<\/span>.<\/span>out.<\/span>println<\/span>(<\/span>"\u6027\u522b\u4e3a：\u7537"<\/span>)<\/span>;<\/span>
    \n }<\/span>
    \n }<\/span><\/p>\n

    }<\/span><\/p>\n

    \u4f5c\u4e1a5：<\/h5>\n

    package<\/span> com.<\/span>itheima.<\/span>testdemo7<\/span>;<\/span><\/p>\n

    import<\/span> java.<\/span>util.<\/span><\/span>Scanner<\/span><\/span>;<\/span><\/p>\n

    public<\/span> class<\/span> Test12<\/span> {<\/span>
    \n public<\/span> static<\/span> void<\/span> main<\/span>(<\/span>String<\/span>[<\/span>]<\/span> args)<\/span> {<\/span>
    \n \/*
    \n \u3010\u6848\u4f8b\u3011\u5b57\u7b26\u4e32\u8f6c\u6362（\u4f5c\u4e1a5）
    \n \u5c06\u4e00\u4e2a\u5b57\u7b26\u4e32\u4e2d\u6240\u6709\u7684\u6574\u6570\u524d\u540e\u52a0\u4e0a\u7b26\u53f7\u201c*\u201d，\u5176\u4ed6\u5b57\u7b26\u4fdd\u6301\u4e0d\u53d8\u3002\u8fde\u7eed\u7684\u6570\u5b57\u89c6\u4e3a\u4e00\u4e2a\u6574\u6570\u3002
    \n \u6570\u636e\u8303\u56f4：\u5b57\u7b26\u4e32\u957f\u5ea6\u6ee1\u8db3 1 \u2264 n \u2264 100
    \n \u8f93\u5165\u63cf\u8ff0：
    \n \u8f93\u5165\u4e00\u4e2a\u5b57\u7b26\u4e32
    \n \u8f93\u51fa\u63cf\u8ff0：
    \n \u5b57\u7b26\u4e2d\u6240\u6709\u51fa\u73b0\u7684\u6570\u5b57\u524d\u540e\u52a0\u4e0a\u7b26\u53f7\u201c*\u201d，\u5176\u4ed6\u5b57\u7b26\u4fdd\u6301\u4e0d\u53d8<\/p>\n

    \u793a\u4f8b1
    \n \u8f93\u5165：
    \n Jkdi234klowe90a3 (\u6ce8：\u6b64\u5904\u6709\u4e00\u4e2a\u9f20\u6807\u5149\u6807)
    \n \u8f93\u51fa：
    \n Jkdi*234*klowe*90*a*3*
    \n *\/<\/span>
    \n Scanner<\/span> sc =<\/span> new<\/span> Scanner<\/span>(<\/span>System<\/span>.<\/span>in)<\/span>;<\/span>
    \n System<\/span>.<\/span>out.<\/span>println<\/span>(<\/span>"\u8bf7\u8f93\u5165\u4e00\u4e2a\u5b57\u7b26\u4e32："<\/span>)<\/span>;<\/span>
    \n String<\/span> str =<\/span> sc.<\/span>nextLine<\/span>(<\/span>)<\/span>;<\/span>
    \n if<\/span>(<\/span>str.<\/span>length<\/span>(<\/span>)<\/span> <<\/span> 1<\/span> ||<\/span> str.<\/span>length<\/span>(<\/span>)<\/span> ><\/span> 100<\/span>)<\/span>{<\/span>
    \n System<\/span>.<\/span>out.<\/span>println<\/span>(<\/span>"\u8f93\u5165\u5b57\u7b26\u4e32\u957f\u5ea6\u8d85\u51fa\u8303\u56f4"<\/span>)<\/span>;<\/span>
    \n }<\/span><\/p>\n

    \/\/\u65b0\u5efa\u4e00\u4e2a\u5b57\u7b26\u4e32\u5bb9\u5668<\/span>
    \n StringBuilder<\/span> sb =<\/span> new<\/span> StringBuilder<\/span>(<\/span>)<\/span>;<\/span>
    \n int<\/span> i =<\/span> 0<\/span>;<\/span>
    \n while<\/span>(<\/span>i <<\/span> str.<\/span>length<\/span>(<\/span>)<\/span>)<\/span>{<\/span>
    \n char<\/span> c =<\/span> str.<\/span>charAt<\/span>(<\/span>i)<\/span>;<\/span>
    \n if<\/span>(<\/span>c >=<\/span> '0'<\/span> &&<\/span> c <=<\/span> '9'<\/span>)<\/span>{<\/span>
    \n \/\/\u9047\u5230\u6570\u5b57，\u5148\u52a0\u524d\u9762\u7684*<\/span>
    \n sb.<\/span>append<\/span>(<\/span>'*'<\/span>)<\/span>;<\/span><\/p>\n

    \/\/\u628a\u8fde\u7eed\u7684\u6570\u5b57\u5168\u90e8\u6570\u5b57\u62fc\u8fdb\u53bb<\/span>
    \n while<\/span>(<\/span>i <<\/span> str.<\/span>length<\/span>(<\/span>)<\/span> &&<\/span> str.<\/span>charAt<\/span>(<\/span>i)<\/span> >=<\/span> '0'<\/span> &&<\/span> str.<\/span>charAt<\/span>(<\/span>i)<\/span> <=<\/span> '9'<\/span>)<\/span>{<\/span>
    \n sb.<\/span>append<\/span>(<\/span>str.<\/span>charAt<\/span>(<\/span>i)<\/span>)<\/span>;<\/span>
    \n i++<\/span>;<\/span>
    \n }<\/span>
    \n \/\/\u8fde\u7eed\u6570\u5b57\u7ed3\u675f\u540e，\u52a0\u540e\u9762\u7684*<\/span>
    \n sb.<\/span>append<\/span>(<\/span>'*'<\/span>)<\/span>;<\/span>
    \n }<\/span>else<\/span>{<\/span>
    \n \/\/\u4e0d\u662f\u6570\u5b57，\u539f\u6837\u62fc\u8fdb\u53bb<\/span>
    \n sb.<\/span>append<\/span>(<\/span>c)<\/span>;<\/span>
    \n i++<\/span>;<\/span>
    \n }<\/span>
    \n }<\/span>
    \n System<\/span>.<\/span>out.<\/span>println<\/span>(<\/span>sb.<\/span>toString<\/span>(<\/span>)<\/span>)<\/span>;<\/span>
    \n }<\/span>
    \n}<\/span><\/p>\n

    \u4f5c\u4e1a6：<\/h5>\n

    package<\/span> com.<\/span>itheima.<\/span>testdemo7<\/span>;<\/span><\/p>\n

    import<\/span> java.<\/span>util.<\/span><\/span>Random<\/span><\/span>;<\/span><\/p>\n

    public<\/span> class<\/span> Test13<\/span> {<\/span>
    \n public<\/span> static<\/span> void<\/span> main<\/span>(<\/span>String<\/span>[<\/span>]<\/span> args)<\/span> {<\/span>
    \n \/*
    \n \u3010\u6848\u4f8b\u3011\u751f\u6210\u9a8c\u8bc1\u7801（\u4f5c\u4e1a6）
    \n \u9a8c\u8bc1\u7801\u7684\u5185\u5bb9：\u53ef\u4ee5\u662f\u5c0f\u5199\u5b57\u6bcd，\u4e5f\u53ef\u4ee5\u662f\u5927\u5199\u5b57\u6bcd，\u8fd8\u53ef\u4ee5\u662f\u6570\u5b57
    \n \u9a8c\u8bc1\u7801\u7684\u89c4\u5219：
    \n \u3000\u3000\u957f\u5ea6\u4e3a5
    \n \u3000\u3000\u5185\u5bb9\u4e2d\u662f\u56db\u4f4d\u5b57\u6bcd，1\u4f4d\u6570\u5b57\u3002
    \n \u3000\u3000\u5176\u4e2d\u6570\u5b57\u53ea\u67091\u4f4d，\u4f46\u662f\u53ef\u4ee5\u51fa\u73b0\u5728\u4efb\u610f\u7684\u4f4d\u7f6e\u3002<\/p>\n

    \u4e3e\u4f8b：
    \n \u6b63\u786e\u7684\u9a8c\u8bc1\u7801：We1fg 6gKoq tqB2p
    \n \u9519\u8bef\u7684\u9a8c\u8bc1\u7801：iuybs（\u6ca1\u6709\u6570\u5b57） j1s2u（\u4e24\u4e2a\u6570\u5b57）
    \n *\/<\/span>
    \n Random<\/span> r =<\/span> new<\/span> Random<\/span>(<\/span>)<\/span>;<\/span>
    \n \/\/1.\u5148\u968f\u673a\u751f\u62105\u4f4d\u5b57\u6bcd(\u5927\u5c0f\u5199\u968f\u673a)<\/span>
    \n StringBuilder<\/span> sb =<\/span> new<\/span> StringBuilder<\/span>(<\/span>)<\/span>;<\/span>
    \n for<\/span>(<\/span>int<\/span> i =<\/span> 0<\/span>;<\/span>i <<\/span> 5<\/span>;<\/span>i++<\/span>)<\/span>{<\/span>
    \n char<\/span> c;<\/span>
    \n if<\/span>(<\/span>r.<\/span>nextBoolean<\/span>(<\/span>)<\/span>)<\/span>{<\/span>\/\/ \u629b\u786c\u5e01，\u6b63\u9762(true)\u8d70\u8fd9\u91cc<\/span>
    \n \/\/\u751f\u6210\u5927\u5199: 'A' + 0~25<\/span>
    \n c =<\/span> (<\/span>char<\/span>)<\/span>(<\/span>'A'<\/span> +<\/span> r.<\/span>nextInt<\/span>(<\/span>26<\/span>)<\/span> )<\/span>;<\/span>
    \n }<\/span>else<\/span>{<\/span> \/\/ \u53cd\u9762(false)\u8d70\u8fd9\u91cc<\/span>
    \n \/\/\u751f\u6210\u5c0f\u5199: 'a' + 0~25<\/span>
    \n c =<\/span> (<\/span>char<\/span>)<\/span> (<\/span>'a'<\/span> +<\/span> r.<\/span>nextInt<\/span>(<\/span>26<\/span>)<\/span>)<\/span>;<\/span>
    \n }<\/span>
    \n sb.<\/span>append<\/span>(<\/span>c)<\/span>;<\/span>
    \n }<\/span>
    \n \/\/2.\u968f\u673a\u4e00\u4e2a\u4f4d\u7f6e(0~4)\u548c\u4e00\u4e2a\u6570\u5b57(0~9),\u628a\u8be5\u4f4d\u7f6e\u8986\u76d6\u6210\u6570\u5b57<\/span>
    \n \/\/setCharAt(\u4f4d\u7f6e, \u65b0\u5b57\u7b26) = \u628a StringBuilder \u91cc\u67d0\u4e2a\u4f4d\u7f6e\u7684\u5b57\u7b26，\u66ff\u6362\u6210\u65b0\u5b57\u7b26<\/span>
    \n int<\/span> index =<\/span> r.<\/span>nextInt<\/span>(<\/span>5<\/span>)<\/span>;<\/span>
    \n int<\/span> num =<\/span> r.<\/span>nextInt<\/span>(<\/span>10<\/span>)<\/span>;<\/span>
    \n sb.<\/span>setCharAt<\/span>(<\/span>index,<\/span> (<\/span>char<\/span>)<\/span>(<\/span>'0'<\/span> +<\/span> num)<\/span>)<\/span>;<\/span>
    \n \/\/3.\u8f93\u51fa\u7ed3\u679c<\/span>
    \n System<\/span>.<\/span>out.<\/span>println<\/span>(<\/span>sb.<\/span>toString<\/span>(<\/span>)<\/span>)<\/span>;<\/span>
    \n }<\/span>
    \n}<\/span><\/p>\n

    \u4f5c\u4e1a7：<\/h5>\n

    package<\/span> com.<\/span>itheima.<\/span>testdemo7<\/span>;<\/span><\/p>\n

    import<\/span> java.<\/span>util.<\/span><\/span>Scanner<\/span><\/span>;<\/span><\/p>\n

    public<\/span> class<\/span> Test14<\/span> {<\/span>
    \n public<\/span> static<\/span> void<\/span> main<\/span>(<\/span>String<\/span>[<\/span>]<\/span> args)<\/span> {<\/span>
    \n \/*
    \n \u6848\u4f8b \u5b57\u7b26\u4e32\u8ba1\u7b97（\u4f5c\u4e1a7）\u3010\u4e0d\u592a\u61c2\u3011
    \n \u952e\u76d8\u8f93\u5165\u4e24\u4e2a\u5b57\u7b26\u4e32\u8868\u793a\u7684\u975e\u8d1f\u6574\u6570，\u6c42\u5b83\u4eec\u7684\u4e58\u79ef\u3002
    \n \u6ce8\u610f： \u9700\u8981\u8003\u8651\u952e\u76d8\u5f55\u5165\u7684\u6570\u636e\u8fc7\u5927，\u8d85\u51faint\u53d6\u503c\u8303\u56f4\u7684
    \n *\/<\/span>
    \n Scanner<\/span> sc =<\/span> new<\/span> Scanner<\/span>(<\/span>System<\/span>.<\/span>in)<\/span>;<\/span>
    \n System<\/span>.<\/span>out.<\/span>println<\/span>(<\/span>"\u8bf7\u8f93\u5165\u4e24\u4e2a\u5b57\u7b26\u4e32\u8868\u793a\u7684\u975e\u8d1f\u6574\u6570："<\/span>)<\/span>;<\/span>
    \n String<\/span> str1 =<\/span> sc.<\/span>nextLine<\/span>(<\/span>)<\/span>;<\/span>
    \n String<\/span> str2 =<\/span> sc.<\/span>nextLine<\/span>(<\/span>)<\/span>;<\/span>
    \n int<\/span> m =<\/span> str1.<\/span>length<\/span>(<\/span>)<\/span>;<\/span>
    \n int<\/span> n =<\/span> str2.<\/span>length<\/span>(<\/span>)<\/span>;<\/span>
    \n \/\/\u4e58\u79ef\u6700\u591a m+n \u4f4d<\/span>
    \n int<\/span>[<\/span>]<\/span> res =<\/span> new<\/span> int<\/span>[<\/span>m +<\/span> n]<\/span>;<\/span>
    \n \/\/\u6a21\u62df\u7ad6\u5f0f\u4e58\u6cd5：\u4ece\u4e24\u4e2a\u6570\u7684\u6700\u4f4e\u4f4d\u5f00\u59cb\u4e24\u4e24\u76f8\u4e58<\/span>
    \n for<\/span> (<\/span>int<\/span> i =<\/span> m –<\/span> 1<\/span>;<\/span> i >=<\/span> 0<\/span>;<\/span> i—<\/span>)<\/span> {<\/span>
    \n int<\/span> d1 =<\/span> str1.<\/span>charAt<\/span>(<\/span>i)<\/span> –<\/span> '0'<\/span>;<\/span>\/\/\u628a\u5b57\u7b26\u8f6c\u6210\u6570\u5b57<\/span>
    \n for<\/span> (<\/span>int<\/span> j =<\/span> n –<\/span> 1<\/span>;<\/span> j >=<\/span> 0<\/span>;<\/span> j—<\/span>)<\/span> {<\/span>
    \n int<\/span> d2 =<\/span> str2.<\/span>charAt<\/span>(<\/span>j)<\/span> –<\/span> '0'<\/span>;<\/span>
    \n int<\/span> mul =<\/span> d1 *<\/span> d2;<\/span>
    \n int<\/span> p1 =<\/span> i +<\/span> j;<\/span> \/\/\u8fdb\u4f4d\u5b58\u653e\u7684\u4f4d\u7f6e(\u9ad8\u4f4d)<\/span>
    \n int<\/span> p2 =<\/span> i +<\/span> j +<\/span> 1<\/span>;<\/span> \/\/\u5f53\u524d\u4f4d\u5b58\u653e\u7684\u4f4d\u7f6e(\u4f4e\u4f4d)<\/span>
    \n int<\/span> sum =<\/span> mul +<\/span> res[<\/span>p2]<\/span>;<\/span>\/\/\u52a0\u4e0a\u8be5\u4f4d\u7f6e\u539f\u6765\u5df2\u7ecf\u7d2f\u79ef\u7684\u503c<\/span>
    \n res[<\/span>p2]<\/span> =<\/span> sum %<\/span> 10<\/span>;<\/span> \/\/\u7559\u4e2a\u4f4d<\/span>
    \n res[<\/span>p1]<\/span> +=<\/span> sum \/<\/span> 10<\/span>;<\/span> \/\/\u8fdb\u4f4d\u7d2f\u52a0\u5230\u9ad8\u4f4d<\/span>
    \n }<\/span>
    \n }<\/span><\/p>\n

    \/\/\u62fc\u63a5\u7ed3\u679c，\u8df3\u8fc7\u5f00\u5934\u76840<\/span>
    \n StringBuilder<\/span> sb =<\/span> new<\/span> StringBuilder<\/span>(<\/span>)<\/span>;<\/span>
    \n boolean<\/span> leading =<\/span> true<\/span>;<\/span>
    \n for<\/span> (<\/span>int<\/span> num :<\/span> res)<\/span> {<\/span>
    \n if<\/span> (<\/span>leading &&<\/span> num ==<\/span> 0<\/span>)<\/span> {<\/span>
    \n continue<\/span>;<\/span>\/\/\u8fd8\u5728\u8df3\u8fc7\u524d\u5bfc\u96f6<\/span>
    \n }<\/span>
    \n leading =<\/span> false<\/span>;<\/span>
    \n sb.<\/span>append<\/span>(<\/span>num)<\/span>;<\/span>
    \n }<\/span>
    \n \/\/\u5982\u679c\u7ed3\u679c\u5168\u662f0(\u4e58\u4e860)，\u90a3\u5c31\u662f"0"<\/span>
    \n String<\/span> result =<\/span> sb.<\/span>length<\/span>(<\/span>)<\/span> ==<\/span> 0<\/span> ?<\/span> "0"<\/span> :<\/span> sb.<\/span>toString<\/span>(<\/span>)<\/span>;<\/span>
    \n System<\/span>.<\/span>out.<\/span>println<\/span>(<\/span>str1 +<\/span> " * "<\/span> +<\/span> str2 +<\/span> " = "<\/span> +<\/span> result)<\/span>;<\/span>
    \n }<\/span>
    \n}<\/span><\/p>\n

    📖\u4eca\u65e5\u77e5\u8bc6\u70b9 \u2014\u2014ArrayList\u96c6\u5408<\/h3>\n

    \u4e00\u3001\u96c6\u5408\u7684\u5f15\u5165：\u6570\u7ec4\u7684\u5f0a\u7aef<\/h4>\n

    Java \u4e2d\u8981\u4fdd\u5b58\u591a\u4e2a\u6570\u636e，\u6700\u5148\u60f3\u5230\u7684\u662f\u6570\u7ec4：<\/p>\n

    \/\/ \u683c\u5f0f：\u6570\u636e\u7c7b\u578b \u6570\u7ec4\u540d[] = {\u6570\u636e\u503c, \u6570\u636e\u503c…}<\/span>
    \nint<\/span> arr[<\/span>]<\/span> =<\/span> {<\/span>1<\/span>,<\/span> 2<\/span>,<\/span> 3<\/span>}<\/span>;<\/span><\/p>\n

    \u6570\u7ec4\u7684\u7279\u70b9：\u4e00\u65e6\u5b9a\u4e49，\u957f\u5ea6\u4e0d\u53ef\u53d8\u3002
    \n\u56e0\u6b64\u6570\u7ec4\u4e2d\u5b58\u5728\u660e\u663e\u5f0a\u7aef：<\/p>\n\n\u573a\u666f\u6570\u7ec4\u7684\u8868\u73b0<\/tr>\n\n\n\n\n
    \u5b9a\u4e49\u65f6\u957f\u5ea6\u5c31\u56fa\u5b9a\u4e86<\/td>\n\u53ea\u80fd\u88c5\u4e0b arr.length \u4e2a\u5143\u7d20，\u591a\u4e86\u88c5\u4e0d\u4e0b\u3001\u5c11\u4e86\u6d6a\u8d39\u7a7a\u95f4<\/td>\n<\/tr>\n
    \u60f3\u5728\u6570\u7ec4\u4e2d\u95f4\u589e\/\u5220\u5143\u7d20<\/td>\n\u505a\u4e0d\u5230，\u53ea\u80fd\u81ea\u5df1\u521b\u5efa\u65b0\u6570\u7ec4\u5e76\u642c\u8fd0\u6570\u636e<\/td>\n<\/tr>\n
    \u4e4b\u524d\u5b9a\u4e49\u7684\u6570\u7ec4\u4e0d\u591f\u7528<\/td>\n\u53ea\u80fd\u91cd\u65b0\u5b9a\u4e49\u4e00\u4e2a\u66f4\u5927\u7684\u6570\u7ec4<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

    \u7ed3\u8bba：\u6570\u7ec4\u9002\u5408"\u6570\u636e\u4e2a\u6570\u786e\u5b9a\u3001\u4ee5\u67e5\u8be2\u4e3a\u4e3b"\u7684\u573a\u666f；\u4e00\u65e6\u9700\u8981\u52a8\u6001\u589e\u5220，\u5c31\u5e94\u8be5\u6539\u7528\u96c6\u5408\u3002<\/p>\n

    \u4e8c\u3001\u4ec0\u4e48\u662f\u96c6\u5408<\/h4>\n

    \u96c6\u5408：\u662f\u4e00\u79cd\u957f\u5ea6\u53ef\u53d8\u7684\u5bb9\u5668\u3002
    \n\u96c6\u5408\u7684\u4e24\u5927\u7279\u70b9：<\/p>\n

      \n
    • \u7279\u70b9 1：\u957f\u5ea6\u53ef\u53d8\u3002 \u6dfb\u52a0\u5143\u7d20\u65f6\u81ea\u52a8\u6269\u5bb9，\u5220\u9664\u5143\u7d20\u540e\u957f\u5ea6\u968f\u4e4b\u53d8\u5c0f，\u4e0d\u7528\u5173\u5fc3\u5bb9\u91cf\u3002<\/li>\n
    • \u7279\u70b9 2：\u53ea\u80fd\u5b58\u5f15\u7528\u6570\u636e\u7c7b\u578b，\u4e0d\u80fd\u5b58\u57fa\u672c\u6570\u636e\u7c7b\u578b\u3002 \u60f3\u5b58 int\u3001double \u7b49\u57fa\u672c\u7c7b\u578b，\u5fc5\u987b\u5148\u7528\u5bf9\u5e94\u7684\u5305\u88c5\u7c7b\u88c5\u7bb1\u3002<\/li>\n<\/ul>\n

      \u6570\u7ec4 vs \u96c6\u5408<\/h4>\n\n\u5bf9\u6bd4\u9879\u6570\u7ec4\u96c6\u5408（ArrayList）<\/tr>\n\n\n\n\n\n
      \u957f\u5ea6<\/td>\n\u5b9a\u4e49\u540e\u4e0d\u53ef\u53d8<\/td>\n\u53ef\u53d8，\u81ea\u52a8\u6269\u5bb9<\/td>\n<\/tr>\n
      \u5b58\u50a8\u7c7b\u578b<\/td>\n\u57fa\u672c\u7c7b\u578b + \u5f15\u7528\u7c7b\u578b\u90fd\u53ef\u4ee5<\/td>\n\u53ea\u80fd\u5b58\u5f15\u7528\u6570\u636e\u7c7b\u578b<\/td>\n<\/tr>\n
      \u529f\u80fd<\/td>\n\u53ea\u6709 length \u5c5e\u6027<\/td>\n\u63d0\u4f9b\u589e\u3001\u5220\u3001\u6539\u3001\u67e5\u7b49\u5927\u91cf\u65b9\u6cd5<\/td>\n<\/tr>\n
      \u4f7f\u7528\u573a\u666f<\/td>\n\u4e2a\u6570\u56fa\u5b9a\u3001\u67e5\u591a\u6539\u5c11<\/td>\n\u4e2a\u6570\u4e0d\u786e\u5b9a\u3001\u9891\u7e41\u589e\u5220<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

      \u4e09\u3001\u57fa\u672c\u6570\u636e\u7c7b\u578b\u5bf9\u5e94\u7684\u5305\u88c5\u7c7b<\/h4>\n

      \u96c6\u5408\u7684\u6cdb\u578b <> \u4e2d\u53ea\u80fd\u5199\u5f15\u7528\u6570\u636e\u7c7b\u578b，\u57fa\u672c\u7c7b\u578b\u8981\u7528"\u5305\u88c5\u7c7b"\u6765\u4ee3\u66ff：<\/p>\n\n\u57fa\u672c\u7c7b\u578b\u5305\u88c5\u7c7b\u57fa\u672c\u7c7b\u578b\u5305\u88c5\u7c7b<\/tr>\n\n\n\n\n\n\n
      byte<\/td>\nByte<\/td>\nfloat<\/td>\nFloat<\/td>\n<\/tr>\n
      short<\/td>\nShort<\/td>\ndouble<\/td>\nDouble<\/td>\n<\/tr>\n
      int<\/td>\nInteger<\/td>\nchar<\/td>\nCharacter<\/td>\n<\/tr>\n
      long<\/td>\nLong<\/td>\nboolean<\/td>\nBoolean<\/td>\n<\/tr>\n
      \u8bb0\u5fc6\u8981\u70b9：<\/td>\n<\/td>\n<\/td>\n<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n
        \n
      • \u9664\u4e86 int \u2192 Integer\u3001char \u2192 Character \u4e24\u4e2a"\u6539\u540d"\u7684，\u5176\u4f59\u90fd\u662f\u9996\u5b57\u6bcd\u5927\u5199\u3002<\/li>\n
      • \u6709\u4e86\u5305\u88c5\u7c7b，ArrayList<Integer> list = new ArrayList<>(); list.add(1); \u8fd9\u6837\u5199\u662f\u5408\u6cd5\u7684\u2014\u20141 \u4f1a\u88ab\u81ea\u52a8\u88c5\u7bb1\u6210 Integer \u5bf9\u8c61（JDK 5 \u4e4b\u540e\u7684\u81ea\u52a8\u88c5\u7bb1\/\u62c6\u7bb1\u673a\u5236）\u3002<\/li>\n<\/ul>\n

        \u56db\u3001\u6613\u9519\u70b9\u4e0e\u8865\u5145<\/h4>\n
      • remove \u6709\u4e24\u4e2a\u91cd\u8f7d，\u6ce8\u610f\u533a\u5206\n
          \n
        • remove(int index)：\u6309\u7d22\u5f15\u5220\u9664，\u53c2\u6570\u662f\u6570\u5b57\u3002<\/li>\n
        • remove(Object o)：\u6309\u5143\u7d20\u5220\u9664，\u53c2\u6570\u662f\u5bf9\u8c61\u3002<\/li>\n
        • \u5f53\u96c6\u5408\u662f ArrayList<Integer> \u65f6，list.remove(1) \u5220\u7684\u662f\u7d22\u5f15 1；\u60f3\u5220\u503c\u4e3a 1 \u7684\u5143\u7d20，\u8981\u5199 list.remove(Integer.valueOf(1))\u3002<\/li>\n<\/ul>\n<\/li>\n
        • size() \u662f\u65b9\u6cd5，length \u662f\u5c5e\u6027\n
            \n
          • \u6570\u7ec4：arr.length<\/li>\n
          • \u96c6\u5408：list.size()<\/li>\n<\/ul>\n<\/li>\n
          • \u7d22\u5f15\u8d8a\u754c：get \/ set \/ add(index, e) \/ remove(index) \u7684\u7d22\u5f15\u5fc5\u987b\u5728 0 ~ size()-1 \u4e4b\u95f4（add \u53ef\u4ee5\u7b49\u4e8e size()，\u5373\u8ffd\u52a0\u5230\u672b\u5c3e），\u5426\u5219\u629b\u51fa IndexOutOfBoundsException\u3002<\/li>\n
          • \u96c6\u5408\u4e0d\u80fd\u5b58\u57fa\u672c\u7c7b\u578b：new ArrayList<int>() \u662f\u7f16\u8bd1\u9519\u8bef，\u5fc5\u987b\u5199 new ArrayList<Integer>()\u3002<\/li>\n
          • \u6253\u5370\u96c6\u5408：\u76f4\u63a5 System.out.println(list) \u8f93\u51fa\u7684\u662f [\u5143\u7d201, \u5143\u7d202, …] \u5f62\u5f0f，ArrayList \u91cd\u5199\u4e86 toString()\u3002<\/li>\n
          • \u904d\u5386\u65b9\u5f0f：\u9664\u4e86\u666e\u901a for + get(i)，\u8fd8\u53ef\u4ee5\u7528\u589e\u5f3a for（for (String s : list)）\u548c\u8fed\u4ee3\u5668 Iterator\u3002<\/li>\n

            \u4e94\u3001\u603b\u7ed3<\/h4>\n
          • \n

            \u4ec0\u4e48\u662f\u96c6\u5408？
            \n\u96c6\u5408\u662f\u4e00\u79cd\u957f\u5ea6\u53ef\u53d8\u7684\u5bb9\u5668\u3002<\/p>\n<\/li>\n

          • \n

            \u96c6\u5408\u6709\u4ec0\u4e48\u7279\u70b9？<\/p>\n

              \n
            • \u7279\u70b9 1：\u957f\u5ea6\u53ef\u53d8\u3002<\/li>\n
            • \u7279\u70b9 2：\u53ea\u80fd\u5b58\u5f15\u7528\u6570\u636e\u7c7b\u578b，\u4e0d\u80fd\u5b58\u57fa\u672c\u6570\u636e\u7c7b\u578b（\u57fa\u672c\u7c7b\u578b\u8981\u7528\u5305\u88c5\u7c7b）\u3002<\/li>\n<\/ul>\n<\/li>\n
            • \n

              \u5982\u4f55\u521b\u5efa\u96c6\u5408\u7684\u5bf9\u8c61？<\/p>\n

              ArrayList<\/span><<\/span>String<\/span>><\/span><\/span> list =<\/span> new<\/span> ArrayList<\/span><<\/span>><\/span><\/span>(<\/span>)<\/span>;<\/span><\/p>\n

              \"\u5728\u8fd9\u91cc\u63d2\u5165\u56fe\u7247\u63cf\u8ff0\"<\/p>\n<\/li>\n

            • \n

              \u96c6\u5408\u7684\u5e38\u89c1\u65b9\u6cd5？
              \n\u589e\u3001\u5220\u3001\u6539\u3001\u67e5 \u2014\u2014 add \/ remove \/ set \/ get \/ size\u3002<\/p>\n<\/li>\n

              💻\u7ec3\u4e60\u4ee3\u7801<\/h3>\n

              package<\/span> com.<\/span>itheima.<\/span>arraylistdemo8<\/span>;<\/span><\/p>\n

              import<\/span> java.<\/span>util.<\/span><\/span>ArrayList<\/span><\/span>;<\/span><\/p>\n

              public<\/span> class<\/span> Test1<\/span> {<\/span>
              \n public<\/span> static<\/span> void<\/span> main<\/span>(<\/span>String<\/span>[<\/span>]<\/span> args)<\/span> {<\/span>
              \n \/*
              \n ArrayList\u96c6\u5408
              \n \u7a7a\u53c2\u6784\u9020：
              \n ArrayList()：\u521b\u5efa\u4e00\u4e2a\u7a7a\u7684ArrayList\u96c6\u5408
              \n \u5e38\u89c1\u65b9\u6cd5：
              \n boolean add(E e)：\u5411\u96c6\u5408\u7684\u672b\u5c3e\u6dfb\u52a0\u6307\u5b9a\u5143\u7d20
              \n void add(int index, E e)：\u5728\u96c6\u5408\u7684\u6307\u5b9a\u4f4d\u7f6e\u63d2\u5165\u6307\u5b9a\u5143\u7d20
              \n boolean remove(E e): \u5220\u9664\u5143\u7d20
              \n E remove(int index): \u5220\u9664\u6307\u5b9a\u4f4d\u7f6e\u7684\u5143\u7d20，\u5e76\u8fd4\u56de\u8be5\u5143\u7d20
              \n E set(int index, E e): \u4fee\u6539\u6307\u5b9a\u4f4d\u7f6e\u7684\u5143\u7d20，\u5e76\u8fd4\u56de\u8be5\u4f4d\u7f6e\u539f\u6765\u7684\u5143\u7d20
              \n E get(int index): \u83b7\u53d6\u5143\u7d20
              \n int size(): \u83b7\u53d6\u96c6\u5408\u4e2d\u5143\u7d20\u7684\u4e2a\u6570<\/p>\n

              *\/<\/span>
              \n \/\/1. \u521b\u5efaArrayList\u96c6\u5408\u5bf9\u8c61<\/span>
              \n \/\/ArrayList list = new ArrayList();<\/span>
              \n ArrayList<\/span><<\/span>String<\/span>><\/span><\/span> list =<\/span> new<\/span> ArrayList<\/span><<\/span>String<\/span>><\/span><\/span>(<\/span>)<\/span>;<\/span>
              \n \/\/2.\u6dfb\u52a0\u5143\u7d20<\/span>
              \n \/\/ \u7ec6\u82821：ArrayList\u7684add\u65b9\u6cd5\u4e0d\u7ba1\u6dfb\u52a0\u4ec0\u4e48\u90fd\u6dfb\u52a0\u6210\u529f，\u5ffd\u7565\u8fd4\u56de\u503c\u5373\u53ef<\/span>
              \n \/\/ true：\u6dfb\u52a0\u6210\u529f false:\u6dfb\u52a0\u5931\u8d25<\/span>
              \n \/\/ \u6b64\u65f6add\u65b9\u6cd5\u5728\u4efb\u610f\u60c5\u51b5\u4e0b，\u90fd\u4f1a\u6dfb\u52a0\u6210\u529f，\u6c38\u8fdc\u4e0d\u4f1a\u5931\u8d25<\/span>
              \n \/\/ \u56e0\u4e3a\u5728Java\u5f53\u4e2d，\u6709\u5f88\u591a\u5f88\u591a\u7684\u96c6\u5408 HashSet（\u5143\u7d20\u8981\u552f\u4e00） aaa(true) aaa(false)<\/span>
              \n \/\/ \u8bbe\u8ba1：\u8ddf\u5176\u4ed6\u7684\u96c6\u5408\u4fdd\u6301\u7edf\u4e00（\u9762\u5411\u5bf9\u8c61\u7684\u601d\u60f3）<\/span><\/p>\n

              \/\/ \u7ec6\u82822：\u5728\u96c6\u5408\u5f53\u4e2d\u65e0\u6cd5\u76f4\u63a5\u6dfb\u52a0\u57fa\u672c\u6570\u636e\u7c7b\u578b\u7684（byte short int long float double char boolean）<\/span>
              \n \/\/ \u53ea\u80fd\u6dfb\u52a0\u5f15\u7528\u6570\u636e\u7c7b\u578b（\u5bf9\u8c61）<\/span>
              \n \/\/ \u5982\u679c\u5728\u96c6\u5408\u91cc\u9762\u4e00\u5b9a\u8981\u6dfb\u52a0\u57fa\u672c\u6570\u636e\u7c7b\u578b，\u90a3\u4e48\u53ef\u4ee5\u8f6c\u6210\u5176\u5bf9\u5e94\u7684\u5305\u88c5\u7c7b<\/span>
              \n list.<\/span>add<\/span>(<\/span>"aaa"<\/span>)<\/span>;<\/span>
              \n list.<\/span>add<\/span>(<\/span>"bbb"<\/span>)<\/span>;<\/span>
              \n list.<\/span>add<\/span>(<\/span>"ccc"<\/span>)<\/span>;<\/span>
              \n \/\/ \u628aqqq\u6dfb\u52a0\u52300\u7d22\u5f15\u7684\u4f4d\u7f6e<\/span>
              \n \/\/ \u7ec6\u8282：<\/span>
              \n \/\/ \u5982\u679c\u96c6\u5408\u957f\u5ea6\u4e3a3，\u90a3\u4e48\u4e0b\u9762\u65b9\u6cd5\u8981\u6dfb\u52a0\u7684\u7d22\u5f15\u8303\u56f4\u53ea\u80fd\u662f0 ~ 3<\/span>
              \n \/\/ 0 – 2 \u5df2\u7ecf\u5b58\u5728\u7684\u7d22\u5f15<\/span>
              \n \/\/ 3：\u628a\u5f53\u524d\u5143\u7d20\u6dfb\u52a0\u5230\u96c6\u5408\u7684\u672b\u5c3e，\u7b49\u540c\u4e8e\u4e00\u4e2a\u53c2\u6570\u7684add\u65b9\u6cd5<\/span>
              \n \/\/ \u5982\u679c\u8981\u6dfb\u52a0\u7684\u7d22\u5f15\u8d85\u51fa\u4e86\u8fd9\u4e2a\u8303\u56f4，\u7a0b\u5e8f\u5c31\u4f1a\u76f4\u63a5\u62a5\u9519<\/span>
              \n list.<\/span>add<\/span>(<\/span>3<\/span>,<\/span>"qqq"<\/span>)<\/span>;<\/span>
              \n System<\/span>.<\/span>out.<\/span>println<\/span>(<\/span>list)<\/span>;<\/span>\/\/[aaa, bbb, ccc, qqq]<\/span><\/p>\n

              \/\/ boolean remove(E e) \u6839\u636e\u5143\u7d20\u5220\u9664<\/span>
              \n \/\/ \u7ec6\u8282：<\/span>
              \n \/\/ \u6839\u636e\u5143\u7d20\u7684\u5185\u5bb9\u8fdb\u884c\u5220\u9664\u7684<\/span>
              \n \/\/ \u5b58\u5728：\u5220\u9664\u6210\u529f true<\/span>
              \n \/\/ \u4e0d\u5b58\u5728：\u5220\u9664\u5931\u8d25 false<\/span>
              \n \/\/boolean res = list.remove("QQQ");<\/span>
              \n \/\/System.out.println(res);<\/span><\/p>\n

              \/\/ E set(int index,E e) \u5c06\u6307\u5b9a\u4f4d\u7f6e\u7684\u6570\u636e，\u4fee\u6539\u4e3a\u65b0\u5143\u7d20<\/span>
              \n \/\/ \u7ec6\u8282：<\/span>
              \n \/\/ \u628a\u6307\u5b9a\u7d22\u5f15\u4e0a\u7684\u6570\u636e\u4fee\u6539\u4e3a\u65b0\u7684\u6570\u636e，\u628a\u88ab\u66ff\u6362\u7684\u5143\u7d20\u8fdb\u884c\u8fd4\u56de<\/span>
              \n \/\/ \u6ce8\u610f：<\/span>
              \n \/\/ \u5982\u679c\u5f53\u524d\u7684\u7d22\u5f15\u4e0d\u5b58\u5728，\u4ee3\u7801\u4f1a\u62a5\u9519<\/span>
              \n \/\/\u628a0\u7d22\u5f15\u7684\u6570\u636e\u4fee\u6539\u4e3a"www"<\/span>
              \n String<\/span> res =<\/span> list.<\/span>set<\/span>(<\/span>0<\/span>,<\/span>"www"<\/span>)<\/span>;<\/span>
              \n System<\/span>.<\/span>out.<\/span>println<\/span>(<\/span>res)<\/span>;<\/span>
              \n System<\/span>.<\/span>out.<\/span>println<\/span>(<\/span>list)<\/span>;<\/span>
              \n \/\/ E get(int index) \u83b7\u53d6\u7279\u5b9a\u7d22\u5f15\u7684\u6570\u636e<\/span>
              \n \/\/ String res = list.get(0);<\/span>
              \n \/\/ System.out.println(res);<\/span><\/p>\n

              \/\/ \u904d\u5386：get + size<\/span>
              \n \/\/ \u904d\u5386：\u628a\u5bb9\u5668\u91cc\u9762\u7684\u6570\u636e\u4e00\u4e2a\u4e00\u4e2a\u7684\u62ff\u51fa\u6765，\u6253\u5370，\u8ba1\u7b97，\u5904\u7406<\/span>
              \n for<\/span> (<\/span>int<\/span> i =<\/span> 0<\/span>;<\/span> i <<\/span> list.<\/span>size<\/span>(<\/span>)<\/span>;<\/span> i++<\/span>)<\/span> {<\/span>
              \n \/\/ i: \u4f9d\u6b21\u8868\u793a\u96c6\u5408\u4e2d\u7684\u6bcf\u4e00\u4e2a\u7d22\u5f15<\/span>
              \n \/\/ list.get(i):\u4f9d\u6b21\u83b7\u53d6\u96c6\u5408\u4e2d\u7684\u6bcf\u4e00\u4e2a\u5143\u7d20<\/span>
              \n System<\/span>.<\/span>out.<\/span>println<\/span>(<\/span>list.<\/span>get<\/span>(<\/span>i)<\/span>)<\/span>;<\/span>
              \n }<\/span>
              \n \/\/ \u53ea\u80fd\u770b\u4e00\u770b\u96c6\u5408\u5f53\u4e2d\u6709\u4ec0\u4e48，\u65e0\u6cd5\u64cd\u4f5c\u91cc\u9762\u7684\u6bcf\u4e00\u4e2a\u5143\u7d20\u7684<\/span>
              \n System<\/span>.<\/span>out.<\/span>println<\/span>(<\/span>list)<\/span>;<\/span><\/p>\n

              }<\/span>
              \n}<\/span><\/p>\n

              \u7ec3\u4e60\u98981：<\/h6>\n

              package<\/span> com.<\/span>itheima.<\/span>arraylistdemo8<\/span>;<\/span><\/p>\n

              import<\/span> java.<\/span>util.<\/span><\/span>ArrayList<\/span><\/span>;<\/span><\/p>\n

              public<\/span> class<\/span> Test2<\/span> {<\/span>
              \n public<\/span> static<\/span> void<\/span> main<\/span>(<\/span>String<\/span>[<\/span>]<\/span> args)<\/span> {<\/span>
              \n \/*
              \n \u9700\u6c42：\u5b9a\u4e49\u4e00\u4e2a\u96c6\u5408，\u6dfb\u52a0\u6570\u5b57，\u5e76\u8fdb\u884c\u904d\u5386
              \n \u904d\u5386\u683c\u5f0f\u53c2\u8003[\u5143\u7d201,\u5143\u7d202,\u5143\u7d203]
              \n *\/<\/span>
              \n \/\/1.\u521b\u5efa\u4e00\u4e2a\u96c6\u5408<\/span>
              \n ArrayList<\/span><<\/span>Integer<\/span>><\/span><\/span> list =<\/span> new<\/span> ArrayList<\/span><<\/span>><\/span><\/span>(<\/span>)<\/span>;<\/span>
              \n \/\/2.\u6dfb\u52a0\u6570\u636e<\/span>
              \n list.<\/span>add<\/span>(<\/span>1<\/span>)<\/span>;<\/span>
              \n list.<\/span>add<\/span>(<\/span>2<\/span>)<\/span>;<\/span>
              \n list.<\/span>add<\/span>(<\/span>3<\/span>)<\/span>;<\/span>
              \n \/\/3.\u904d\u5386\u6570\u636e<\/span>
              \n System<\/span>.<\/span>out.<\/span>print<\/span>(<\/span>"["<\/span>)<\/span>;<\/span>
              \n for<\/span> (<\/span>int<\/span> i =<\/span> 0<\/span>;<\/span> i <<\/span> list.<\/span>size<\/span>(<\/span>)<\/span>;<\/span> i++<\/span>)<\/span> {<\/span>
              \n \/\/i:\u7d22\u5f15<\/span>
              \n \/\/list.get(i):\u83b7\u53d6\u7d22\u5f15i\u4f4d\u7f6e\u7684\u5143\u7d20<\/span>
              \n Integer<\/span> num =<\/span> list.<\/span>get<\/span>(<\/span>i)<\/span>;<\/span>
              \n if<\/span>(<\/span>i ==<\/span> list.<\/span>size<\/span>(<\/span>)<\/span> –<\/span> 1<\/span>)<\/span>{<\/span>
              \n System<\/span>.<\/span>out.<\/span>print<\/span>(<\/span>num)<\/span>;<\/span>
              \n }<\/span>else<\/span>{<\/span>
              \n System<\/span>.<\/span>out.<\/span>print<\/span>(<\/span>num +<\/span> ","<\/span>)<\/span>;<\/span>
              \n }<\/span>
              \n }<\/span>
              \n System<\/span>.<\/span>out.<\/span>println<\/span>(<\/span>"]"<\/span>)<\/span>;<\/span>
              \n }<\/span>
              \n}<\/span><\/p>\n

              \u7ec3\u4e60\u98982：<\/h6>\n

              package<\/span> com.<\/span>itheima.<\/span>arraylistdemo8<\/span>;<\/span><\/p>\n

              public<\/span> class<\/span> Student<\/span> {<\/span>
              \n \/\/\u5c5e\u6027：id, \u59d3\u540d, \u5e74\u9f84<\/span>
              \n private<\/span> String<\/span> id;<\/span>
              \n private<\/span> String<\/span> name;<\/span>
              \n private<\/span> int<\/span> age;<\/span>
              \n \/\/\u65e0\u53c2\u6784\u9020\u65b9\u6cd5<\/span>
              \n public<\/span> Student<\/span>(<\/span>)<\/span> {<\/span>
              \n }<\/span>
              \n \/\/\u6709\u53c2\u6784\u9020\u65b9\u6cd5<\/span>
              \n public<\/span> Student<\/span>(<\/span>String<\/span> id,<\/span> String<\/span> name,<\/span> int<\/span> age)<\/span> {<\/span>
              \n this<\/span>.<\/span>id =<\/span> id;<\/span>
              \n this<\/span>.<\/span>name =<\/span> name;<\/span>
              \n this<\/span>.<\/span>age =<\/span> age;<\/span>
              \n }<\/span>
              \n \/\/getters and setters<\/span>
              \n public<\/span> String<\/span> getId<\/span>(<\/span>)<\/span> {<\/span>
              \n return<\/span> id;<\/span>
              \n }<\/span>
              \n public<\/span> void<\/span> setId<\/span>(<\/span>String<\/span> id)<\/span> {<\/span>
              \n this<\/span>.<\/span>id =<\/span> id;<\/span>
              \n }<\/span>
              \n public<\/span> String<\/span> getName<\/span>(<\/span>)<\/span> {<\/span>
              \n return<\/span> name;<\/span>
              \n }<\/span>
              \n public<\/span> void<\/span> setName<\/span>(<\/span>String<\/span> name)<\/span> {<\/span>
              \n this<\/span>.<\/span>name =<\/span> name;<\/span>
              \n }<\/span>
              \n public<\/span> int<\/span> getAge<\/span>(<\/span>)<\/span> {<\/span>
              \n return<\/span> age;<\/span>
              \n }<\/span>
              \n public<\/span> void<\/span> setAge<\/span>(<\/span>int<\/span> age)<\/span> {<\/span>
              \n this<\/span>.<\/span>age =<\/span> age;<\/span>
              \n }<\/span>
              \n}<\/span><\/p>\n

              package<\/span> com.<\/span>itheima.<\/span>arraylistdemo8<\/span>;<\/span><\/p>\n

              import<\/span> java.<\/span>util.<\/span><\/span>ArrayList<\/span><\/span>;<\/span><\/p>\n

              public<\/span> class<\/span> Test3<\/span> {<\/span>
              \n public<\/span> static<\/span> void<\/span> main<\/span>(<\/span>String<\/span>[<\/span>]<\/span> args)<\/span> {<\/span>
              \n \/*
              \n \u9700\u6c42：\u5b9a\u4e49\u4e00\u4e2a\u96c6\u5408，\u6dfb\u52a0\u4e00\u4e9b\u5b66\u751f\u5bf9\u8c61
              \n \u5b66\u751f\u7c7b\u7684\u5c5e\u6027\u4e3a：id, \u59d3\u540d, \u5e74\u9f84\u3002
              \n \u8981\u6c42：
              \n 1. \u904d\u5386\u96c6\u5408，\u5c06\u6240\u6709\u5b66\u751f\u7684\u5c5e\u6027\u6253\u5370\u5728\u63a7\u5236\u53f0\u4e0a，\u6bcf\u4e2a\u5b66\u751f\u4e00\u884c
              \n 2. \u5b9a\u4e49\u4e00\u4e2a\u65b9\u6cd5，\u6839\u636eid\u67e5\u627e\u5b66\u751f\u7684\u4fe1\u606f\u3002
              \n \u5b58\u5728：\u8fd4\u56de\u7d22\u5f15
              \n \u4e0d\u5b58\u5728：\u8fd4\u56de-1
              \n *\/<\/span>
              \n \/\/ 1. \u521b\u5efa\u96c6\u5408\u5bf9\u8c61<\/span>
              \n ArrayList<\/span><<\/span>Student<\/span>><\/span><\/span> list =<\/span> new<\/span> ArrayList<\/span><<\/span>><\/span><\/span>(<\/span>)<\/span>;<\/span>
              \n \/\/2.\u521b\u5efa\u4e00\u4e9b\u5b66\u751f\u7684\u5bf9\u8c61<\/span>
              \n \/\/ ALT + \u9f20\u6807\u5de6\u952e \u7ad6\u7740\u9009\u4e2d<\/span>
              \n Student<\/span> s1 =<\/span> new<\/span> Student<\/span>(<\/span>"001"<\/span>,<\/span> "\u5f20\u4e09"<\/span>,<\/span> 18<\/span>)<\/span>;<\/span>
              \n Student<\/span> s2 =<\/span> new<\/span> Student<\/span>(<\/span>"002"<\/span>,<\/span> "\u674e\u56db"<\/span>,<\/span> 19<\/span>)<\/span>;<\/span>
              \n Student<\/span> s3 =<\/span> new<\/span> Student<\/span>(<\/span>"003"<\/span>,<\/span> "\u738b\u4e94"<\/span>,<\/span> 20<\/span>)<\/span>;<\/span>
              \n \/\/3.\u6dfb\u52a0\u5230\u96c6\u5408<\/span>
              \n list.<\/span>add<\/span>(<\/span>s1)<\/span>;<\/span>
              \n list.<\/span>add<\/span>(<\/span>s2)<\/span>;<\/span>
              \n list.<\/span>add<\/span>(<\/span>s3)<\/span>;<\/span>
              \n \/\/4.\u904d\u5386\u96c6\u5408<\/span>
              \n for<\/span> (<\/span>int<\/span> i =<\/span> 0<\/span>;<\/span> i <<\/span> list.<\/span>size<\/span>(<\/span>)<\/span>;<\/span> i++<\/span>)<\/span> {<\/span>
              \n Student<\/span> s =<\/span> list.<\/span>get<\/span>(<\/span>i)<\/span>;<\/span>
              \n System<\/span>.<\/span>out.<\/span>println<\/span>(<\/span>s.<\/span>getId<\/span>(<\/span>)<\/span> +<\/span> " "<\/span> +<\/span> s.<\/span>getName<\/span>(<\/span>)<\/span> +<\/span> " "<\/span> +<\/span> s.<\/span>getAge<\/span>(<\/span>)<\/span>)<\/span>;<\/span>
              \n }<\/span>
              \n \/\/5.\u67e5\u627e\u5bf9\u5e94\u7684id<\/span>
              \n int<\/span> index =<\/span> findStudent<\/span>(<\/span>"002"<\/span>,<\/span> list)<\/span>;<\/span>
              \n System<\/span>.<\/span>out.<\/span>println<\/span>(<\/span>index)<\/span>;<\/span>
              \n }<\/span>
              \n public<\/span> static<\/span> int<\/span> findStudent<\/span>(<\/span>String<\/span> id,<\/span>ArrayList<\/span><<\/span>Student<\/span>><\/span><\/span> list)<\/span>{<\/span>
              \n \/\/\u904d\u5386\u96c6\u5408\u5f97\u5230\u96c6\u5408\u4e2d\u7684\u6bcf\u4e00\u4e2a\u5143\u7d20（\u5b66\u751f\u5bf9\u8c61），\u5224\u65ad\u5143\u7d20\u7684id\u8ddf\u8981\u67e5\u627e\u7684id\u662f\u5426\u4e00\u81f4<\/span>
              \n for<\/span> (<\/span>int<\/span> i =<\/span> 0<\/span>;<\/span> i <<\/span> list.<\/span>size<\/span>(<\/span>)<\/span>;<\/span> i++<\/span>)<\/span> {<\/span>
              \n Student<\/span> s =<\/span> list.<\/span>get<\/span>(<\/span>i)<\/span>;<\/span>
              \n \/\/\u5224\u65adequals — \u94fe\u5f0f\u7f16\u7a0b，\u591a\u884c\u4ee3\u7801\u5199\u5728\u4e00\u884c（\u5c11\u5b9a\u4e49\u51e0\u4e2a\u53d8\u91cf<\/span>
              \n \/\/\u94fe\u5f0f\u7f16\u7a0b\u6838\u5fc3\u70b9：\u5229\u7528\u524d\u4e00\u4e2a\u65b9\u6cd5\u7684\u7ed3\u679c，\u7ee7\u7eed\u8c03\u7528\u540e\u9762\u7684\u5185\u5bb9<\/span>
              \n if<\/span>(<\/span>s.<\/span>getId<\/span>(<\/span>)<\/span>.<\/span>equals<\/span>(<\/span>id)<\/span>)<\/span>{<\/span>
              \n return<\/span> i;<\/span>
              \n }<\/span>
              \n }<\/span>
              \n \/\/\u53ea\u6709\u5f53\u5faa\u73af\u7ed3\u675f\u4e86，\u624d\u8868\u793a\u96c6\u5408\u4e2d\u7684\u6240\u6709\u5143\u7d20\u627e\u5b8c，\u5982\u679c\u8fd8\u6ca1\u6709\u627e\u5230，\u8868\u793a\u8981\u67e5\u627e\u7684id\u4e0d\u5b58\u5728<\/span>
              \n return<\/span> –<\/span>1<\/span>;<\/span>
              \n }<\/span>
              \n}<\/span><\/p>\n","protected":false},"excerpt":{"rendered":"

              \/* MD \/ \u5bcc\u6587\u672c\u4e2d\u7684 .toc\uff08\u542b\u535a\u5ba2\u56ed\u642c\u5bb6\u7b49\u5d4c\u5957\u7ed3\u6784\uff09\uff1b.toc-box \u5728\u4fa7\u680f\uff0c\u4e0d\u53d7\u5f71\u54cd *\/#content_views .toc,\/* \u7f16\u8f91\u5668\u5e38\u5728\u76ee\u5f55\u524d\u540e\u63d2\u5165\u7a7a p\uff08:empty \u4ecd\u5360 20px\uff09\uff0c\u4e00\u5e76\u53bb\u6389\u907f\u514d\u9876\u7a7a\u9699 *\/#content_views.markdown_views > p:empty:has(+ .toc),#content_views.markdown_views > .toc + p:empty,\/* \u5bcc\u6587\u672c\u65e7\u7248\u76ee\u5f55\u6807\u8bb0 *\/#content<\/p>\n","protected":false},"author":2,"featured_media":122461,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[1],"tags":[99,371,123,190,305],"topic":[],"class_list":["post-122464","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-server","tag-java","tag-371","tag-123","tag-190","tag-305"],"yoast_head":"\n\u4e00\u5929\u5403\u900f String \u4e0e StringBuilder\uff1a\u4ece API \u6587\u6863\u5230\u5b57\u7b26\u4e32\u5927\u6570\u76f8\u52a0 - \u7f51\u7855\u4e92\u8054\u5e2e\u52a9\u4e2d\u5fc3<\/title>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/www.wsisp.com\/helps\/122464.html\" \/>\n<meta property=\"og:locale\" content=\"zh_CN\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"\u4e00\u5929\u5403\u900f String \u4e0e StringBuilder\uff1a\u4ece API \u6587\u6863\u5230\u5b57\u7b26\u4e32\u5927\u6570\u76f8\u52a0 - \u7f51\u7855\u4e92\u8054\u5e2e\u52a9\u4e2d\u5fc3\" \/>\n<meta property=\"og:description\" content=\"\/* MD \/ \u5bcc\u6587\u672c\u4e2d\u7684 .toc\uff08\u542b\u535a\u5ba2\u56ed\u642c\u5bb6\u7b49\u5d4c\u5957\u7ed3\u6784\uff09\uff1b.toc-box \u5728\u4fa7\u680f\uff0c\u4e0d\u53d7\u5f71\u54cd *\/#content_views .toc,\/* \u7f16\u8f91\u5668\u5e38\u5728\u76ee\u5f55\u524d\u540e\u63d2\u5165\u7a7a p\uff08:empty \u4ecd\u5360 20px\uff09\uff0c\u4e00\u5e76\u53bb\u6389\u907f\u514d\u9876\u7a7a\u9699 *\/#content_views.markdown_views > p:empty:has(+ .toc),#content_views.markdown_views > .toc + p:empty,\/* \u5bcc\u6587\u672c\u65e7\u7248\u76ee\u5f55\u6807\u8bb0 *\/#content\" \/>\n<meta property=\"og:url\" content=\"https:\/\/www.wsisp.com\/helps\/122464.html\" \/>\n<meta property=\"og:site_name\" content=\"\u7f51\u7855\u4e92\u8054\u5e2e\u52a9\u4e2d\u5fc3\" \/>\n<meta property=\"article:published_time\" content=\"2026-11-04T15:41:09+00:00\" \/>\n<meta property=\"og:image\" content=\"https:\/\/www.wsisp.com\/helps\/wp-content\/uploads\/2026\/11\/20261104154107-6aeb52139a4a3.jpg\" \/>\n<meta name=\"author\" content=\"admin\" \/>\n<meta name=\"twitter:card\" content=\"summary_large_image\" \/>\n<meta name=\"twitter:label1\" content=\"\u4f5c\u8005\" \/>\n\t<meta name=\"twitter:data1\" content=\"admin\" \/>\n\t<meta name=\"twitter:label2\" content=\"\u9884\u8ba1\u9605\u8bfb\u65f6\u95f4\" \/>\n\t<meta name=\"twitter:data2\" content=\"19 \u5206\" \/>\n<script type=\"application\/ld+json\" class=\"yoast-schema-graph\">{\"@context\":\"https:\/\/schema.org\",\"@graph\":[{\"@type\":\"WebPage\",\"@id\":\"https:\/\/www.wsisp.com\/helps\/122464.html\",\"url\":\"https:\/\/www.wsisp.com\/helps\/122464.html\",\"name\":\"\u4e00\u5929\u5403\u900f String \u4e0e StringBuilder\uff1a\u4ece API \u6587\u6863\u5230\u5b57\u7b26\u4e32\u5927\u6570\u76f8\u52a0 - 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