\u76ee\u5f55<\/p>\n
\u4e00\u3001\u524d\u8a00\u7b80\u4ecb<\/p>\n
\u4e8c\u3001\u80cc\u666f\u8bf4\u660e<\/p>\n
\u4e09\u3001\u4f4e\u6548\u65b9\u5f0f<\/p>\n
\u56db\u3001\u9ad8\u6548\u65b9\u5f0f<\/p>\n
\u4e94\u3001\u6027\u80fd\u5bf9\u6bd4<\/p>\n
\u516d\u3001\u6ce8\u610f\u4e8b\u9879<\/p>\n
\u4e03\u3001\u603b\u7ed3\u5f52\u7eb3<\/p>\n
\u00a0 \u00a0 \u00a0 \u00a0\u5728Java\u4e2d，\u5b57\u7b26\u4e32\u62fc\u63a5\u662f\u4e00\u4e2a\u5e38\u89c1\u7684\u64cd\u4f5c，\u4f46\u4e0d\u540c\u7684\u62fc\u63a5\u65b9\u5f0f\u5bf9\u6027\u80fd\u7684\u5f71\u54cd\u5f88\u5927\u3002\u7279\u522b\u662f\u5728\u5faa\u73af\u4e2d\u8fdb\u884c\u5b57\u7b26\u4e32\u62fc\u63a5\u65f6，\u9009\u62e9\u5408\u9002\u7684\u5de5\u5177\u53ef\u4ee5\u663e\u8457\u63d0\u9ad8\u6027\u80fd\u3002<\/p>\n
\u00a0 \u00a0 \u00a0 \u00a0\u5728Java\u4e2d，`String` \u662f\u4e0d\u53ef\u53d8\u7684（immutable）\u3002\u8fd9\u610f\u5473\u7740\u6bcf\u6b21\u5bf9\u5b57\u7b26\u4e32\u8fdb\u884c\u4fee\u6539（\u5982\u62fc\u63a5）\u65f6，\u90fd\u4f1a\u521b\u5efa\u4e00\u4e2a\u65b0\u7684\u5b57\u7b26\u4e32\u5bf9\u8c61\u3002\u4f8b\u5982：<\/p>\n
String s = "a";
\ns += "b"; \/\/ \u5b9e\u9645\u4e0a\u662f s = new String("ab"); <\/p>\n
\u00a0 \u00a0 \u00a0 \u00a0\u6bcf\u6b21\u4f7f\u7528 `+` \u64cd\u4f5c\u7b26\u62fc\u63a5\u5b57\u7b26\u4e32\u65f6，\u90fd\u4f1a\u521b\u5efa\u4e00\u4e2a\u65b0\u7684 `String` \u5bf9\u8c61\u3002<\/p>\n
\u00a0 \u00a0 \u00a0 \u00a0\u5728\u5faa\u73af\u4e2d\u4f7f\u7528 `+` \u64cd\u4f5c\u7b26\u62fc\u63a5\u5b57\u7b26\u4e32\u662f\u975e\u5e38\u4f4e\u6548\u7684，\u56e0\u4e3a\u6bcf\u6b21\u62fc\u63a5\u90fd\u4f1a\u521b\u5efa\u4e00\u4e2a\u65b0\u7684\u5b57\u7b26\u4e32\u5bf9\u8c61，\u5bfc\u81f4\u5927\u91cf\u7684\u4e34\u65f6\u5bf9\u8c61\u4ea7\u751f\u3002\u8fd9\u4e9b\u4e34\u65f6\u5bf9\u8c61\u4f1a\u5360\u7528\u5185\u5b58，\u5e76\u4e14\u9700\u8981\u5783\u573e\u56de\u6536\u5668（GC）\u6765\u6e05\u7406，\u4ece\u800c\u589e\u52a0\u7cfb\u7edf\u7684\u5f00\u9500\u3002<\/p>\n
\u793a\u4f8b\u4ee3\u7801：<\/span><\/p>\n String s = ""; \u6bcf\u6b21\u6267\u884c `s += i` \u65f6，\u5b9e\u9645\u4e0a\u4f1a\u6267\u884c\u4ee5\u4e0b\u6b65\u9aa4： 1. \u521b\u5efa\u4e00\u4e2a\u65b0\u7684 `StringBuilder` \u5bf9\u8c61，\u521d\u59cb\u5316\u4e3a\u5f53\u524d\u7684 `s`\u3002 2. \u8c03\u7528 `StringBuilder` \u7684 `append` \u65b9\u6cd5，\u5c06 `i` \u6dfb\u52a0\u5230 `StringBuilder` \u4e2d\u3002 3. \u8c03\u7528 `StringBuilder` \u7684 `toString` \u65b9\u6cd5，\u751f\u6210\u4e00\u4e2a\u65b0\u7684 `String` \u5bf9\u8c61\u3002 4. \u5c06\u65b0\u751f\u6210\u7684 `String` \u5bf9\u8c61\u8d4b\u503c\u7ed9 `s`\u3002<\/p>\n \u56e0\u6b64，\u6bcf\u6b21\u5faa\u73af\u90fd\u4f1a\u521b\u5efa\u4e00\u4e2a\u65b0\u7684 `StringBuilder` \u548c\u4e00\u4e2a\u65b0\u7684 `String` \u5bf9\u8c61，\u5bfc\u81f4\u6027\u80fd\u4f4e\u4e0b\u3002<\/p>\n \u00a0 \u00a0 \u00a0 \u00a0\u4e3a\u4e86\u63d0\u9ad8\u5b57\u7b26\u4e32\u62fc\u63a5\u7684\u6027\u80fd，Java\u63d0\u4f9b\u4e86 `StringBuilder` \u7c7b（\u4eceJava 5\u5f00\u59cb\u5f15\u5165）\u3002\u5e76\u4e14，`StringBuilder` \u662f\u4e00\u4e2a\u53ef\u53d8\u7684\u5b57\u7b26\u5e8f\u5217，\u5b83\u5141\u8bb8\u5728\u540c\u4e00\u4e2a\u5bf9\u8c61\u4e0a\u8fdb\u884c\u591a\u6b21\u4fee\u6539，\u800c\u4e0d\u9700\u8981\u6bcf\u6b21\u90fd\u521b\u5efa\u65b0\u7684\u5bf9\u8c61\u3002<\/p>\n \u793a\u4f8b\u4ee3\u7801：<\/span><\/p>\n StringBuilder sb = new StringBuilder(); \u5728\u8fd9\u4e2a\u4f8b\u5b50\u4e2d： 1. \u521b\u5efa\u4e86\u4e00\u4e2a `StringBuilder` \u5bf9\u8c61 `sb`\u3002 2. \u5728\u5faa\u73af\u4e2d，\u6bcf\u6b21\u8c03\u7528 `sb.append(i)`，\u90fd\u4f1a\u5c06 `i` \u6dfb\u52a0\u5230 `StringBuilder` \u7684\u5f53\u524d\u5185\u5bb9\u4e2d，\u800c\u4e0d\u4f1a\u521b\u5efa\u65b0\u7684\u5bf9\u8c61\u3002 3. \u6700\u540e，\u8c03\u7528 `sb.toString()` \u751f\u6210\u6700\u7ec8\u7684\u5b57\u7b26\u4e32\u3002<\/p>\n （1）\u4f7f\u7528 `+` \u64cd\u4f5c\u7b26：<\/span><\/p>\n \u6bcf\u6b21\u62fc\u63a5\u90fd\u4f1a\u521b\u5efa\u4e00\u4e2a\u65b0\u7684 `StringBuilder` \u548c\u4e00\u4e2a\u65b0\u7684 `String` \u5bf9\u8c61\u3002<\/p>\n<\/li>\n \u65f6\u95f4\u590d\u6742\u5ea6\u4e3a \\\\(O(n^2)\\\\)，\u56e0\u4e3a\u6bcf\u6b21\u62fc\u63a5\u90fd\u9700\u8981\u590d\u5236\u6574\u4e2a\u5b57\u7b26\u4e32\u3002<\/p>\n<\/li>\n \u4ea7\u751f\u5927\u91cf\u7684\u4e34\u65f6\u5bf9\u8c61，\u589e\u52a0\u5185\u5b58\u5f00\u9500\u548c\u5783\u573e\u56de\u6536\u7684\u8d1f\u62c5\u3002<\/p>\n<\/li>\n<\/ul>\n （2）\u4f7f\u7528 `StringBuilder`：<\/span><\/p>\n \u53ea\u521b\u5efa\u4e00\u4e2a `StringBuilder` \u5bf9\u8c61\u3002<\/p>\n<\/li>\n \u6bcf\u6b21\u8c03\u7528 `append` \u65b9\u6cd5\u65f6，\u76f4\u63a5\u5728\u540c\u4e00\u4e2a\u5bf9\u8c61\u4e0a\u8fdb\u884c\u4fee\u6539，\u4e0d\u9700\u8981\u521b\u5efa\u65b0\u7684\u5bf9\u8c61\u3002<\/p>\n<\/li>\n \u65f6\u95f4\u590d\u6742\u5ea6\u4e3a \\\\(O(n)\\\\)，\u56e0\u4e3a\u6bcf\u6b21\u62fc\u63a5\u53ea\u9700\u8981\u5e38\u6570\u65f6\u95f4\u3002<\/p>\n<\/li>\n \u4ea7\u751f\u8f83\u5c11\u7684\u4e34\u65f6\u5bf9\u8c61，\u51cf\u5c11\u5185\u5b58\u5f00\u9500\u548c\u5783\u573e\u56de\u6536\u7684\u8d1f\u62c5\u3002<\/p>\n<\/li>\n<\/ul>\n （1）`StringBuffer`：<\/span>`StringBuffer` \u4e0e `StringBuilder` \u7c7b\u4f3c，\u4f46\u5b83\u662f\u7ebf\u7a0b\u5b89\u5168\u7684\u3002\u56e0\u6b64，`StringBuffer` \u7684\u6027\u80fd\u6bd4 `StringBuilder` \u7a0d\u5dee，\u56e0\u4e3a\u5b83\u9700\u8981\u8fdb\u884c\u540c\u6b65\u64cd\u4f5c\u3002\u5728\u5355\u7ebf\u7a0b\u73af\u5883\u4e2d，\u63a8\u8350\u4f7f\u7528 `StringBuilder`\u3002 （2）\u5b57\u7b26\u4e32\u5b57\u9762\u91cf\u62fc\u63a5：<\/span>\u5728\u7f16\u8bd1\u65f6，\u5b57\u7b26\u4e32\u5b57\u9762\u91cf\u7684\u62fc\u63a5\u4f1a\u88ab\u4f18\u5316\u3002\u4f8b\u5982：<\/p>\n \u00a0 String s = "a" + "b"; \/\/ \u7f16\u8bd1\u65f6\u4f1a\u88ab\u4f18\u5316\u4e3a "ab" <\/p>\n \u4f46\u662f，\u8fd9\u79cd\u4f18\u5316\u53ea\u9002\u7528\u4e8e\u5b57\u7b26\u4e32\u5b57\u9762\u91cf，\u4e0d\u9002\u7528\u4e8e\u53d8\u91cf\u3002<\/p>\n \u4f4e\u6548\u65b9\u5f0f：\u5728\u5faa\u73af\u4e2d\u4f7f\u7528 `+` \u64cd\u4f5c\u7b26\u62fc\u63a5\u5b57\u7b26\u4e32，\u4f1a\u4ea7\u751f\u5927\u91cf\u4e34\u65f6\u5bf9\u8c61，\u5bfc\u81f4\u6027\u80fd\u4f4e\u4e0b\u3002<\/p>\n<\/li>\n \u9ad8\u6548\u65b9\u5f0f：\u4f7f\u7528 `StringBuilder` \u8fdb\u884c\u5b57\u7b26\u4e32\u62fc\u63a5，\u53ef\u4ee5\u663e\u8457\u63d0\u9ad8\u6027\u80fd，\u51cf\u5c11\u5185\u5b58\u5f00\u9500\u548c\u5783\u573e\u56de\u6536\u7684\u8d1f\u62c5\u3002<\/p>\n<\/li>\n \u63a8\u8350：\u5728\u9700\u8981\u9891\u7e41\u8fdb\u884c\u5b57\u7b26\u4e32\u62fc\u63a5\u7684\u573a\u666f\u4e2d，\u4f18\u5148\u4f7f\u7528 `StringBuilder`\u3002<\/p>\n<\/li>\n<\/ul>\n","protected":false},"excerpt":{"rendered":" \u6587\u7ae0\u6d4f\u89c8\u9605\u8bfb148\u6b21\u3002\u5728Java\u4e2d\uff0c\u5b57\u7b26\u4e32\u62fc\u63a5\u662f\u4e00\u4e2a\u5e38\u89c1\u7684\u64cd\u4f5c\uff0c\u4f46\u4e0d\u540c\u7684\u62fc\u63a5\u65b9\u5f0f\u5bf9\u6027\u80fd\u7684\u5f71\u54cd\u5f88\u5927\u3002\u7279\u522b\u662f\u5728\u5faa\u73af\u4e2d\u8fdb\u884c\u5b57\u7b26\u4e32\u62fc\u63a5\u65f6\uff0c\u9009\u62e9\u5408\u9002\u7684\u5de5\u5177\u53ef\u4ee5\u663e\u8457\u63d0\u9ad8\u6027\u80fd\u3002\u672c\u6587\u4ecb\u7ecd\u5176\u8be6\u7ec6\u4fe1\u606f\u3002<\/p>\n","protected":false},"author":2,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[1],"tags":[99,427],"topic":[],"class_list":["post-58396","post","type-post","status-publish","format-standard","hentry","category-server","tag-java","tag-427"],"yoast_head":"\n
\nfor (int i = 0; i < 100; i++) {
\n\u00a0 \u00a0 s += i; \/\/ \u7b49\u4ef7\u4e8e s = new StringBuilder(s).append(i).toString()
\n} <\/p>\n\u56db\u3001\u9ad8\u6548\u65b9\u5f0f<\/h2>\n
\nfor (int i = 0; i < 100; i++) {
\n\u00a0 \u00a0 sb.append(i);
\n}
\nString result = sb.toString(); <\/p>\n\u4e94\u3001\u6027\u80fd\u5bf9\u6bd4<\/h2>\n
\n
\n
\u516d\u3001\u6ce8\u610f\u4e8b\u9879<\/h2>\n
\u4e03\u3001\u603b\u7ed3\u5f52\u7eb3<\/h2>\n
\n