\u672c\u6587\u8bb2\u8ff0\u6cdb\u578b\u7684\u6982\u5ff5\u3001\u6cdb\u578b\u7684\u5e94\u7528\u573a\u666f，\u8ba9\u6211\u4eec\u66f4\u4e86\u89e3\u6cdb\u578b\u7684\u4f5c\u7528<\/p>\n
\u76ee\u5f55<\/p>\n
\u4e00\u3001\u6cdb\u578b\u7684\u6982\u5ff5<\/p>\n
1\u3001\u4ec0\u4e48\u662f\u6cdb\u578b<\/p>\n
2\u3001\u6cdb\u578b\u7684\u597d\u5904<\/p>\n
3\u3001\u6cdb\u578b\u7684\u76f8\u5173\u540d\u8bcd<\/p>\n
4\u3001\u7c7b\u578b\u53d8\u91cf<\/p>\n
\u7684\u5e94\u7528\u573a\u666f\n <\/p>\n
\u4e8c\u3001\u6cdb\u578b\u7684\u5e94\u7528\u573a\u666f<\/p>\n
1\u3001\u6cdb\u578b\u7c7b\u4e0e\u6cdb\u578b\u63a5\u53e3<\/p>\n
2\u3001\u6cdb\u578b\u65b9\u6cd5<\/p>\n
3\u3001\u7c7b\u578b\u901a\u914d\u7b26<\/p>\n
3.1\u3001\u4e3a\u4ec0\u4e48\u9700\u8981\u901a\u914d\u7b26<\/p>\n
3.2\u3001\u4f5c\u7528<\/p>\n
3.3\u3001\u7c7b\u578b\u901a\u914d\u7b26\u7684\u5206\u7c7b<\/p>\n
3.4\u3001\u4e0a\u9650\u901a\u914d\u7b26<\/p>\n
3.5\u3001\u4e0b\u9650\u901a\u914d\u7b26<\/p>\n
\u4e09\u3001\u53ef\u53d8\u53c2\u6570<\/p>\n
1\u3001\u683c\u5f0f<\/p>\n
2\u3001\u53ef\u53d8\u53c2\u6570\u7684\u5e94\u7528\u573a\u666f<\/p>\n
\u603b\u7ed3<\/p>\n
\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u4f8b\u5982：\u751f\u4ea7\u74f6\u5b50\u7684\u5382\u5bb6，\u4e00\u5f00\u59cb\u5e76\u4e0d\u77e5\u9053\u6211\u4eec\u5c06\u6765\u4f1a\u7528\u74f6\u5b50\u88c5\u4ec0\u4e48，\u6211\u4eec\u4ec0\u4e48\u90fd\u53ef\u4ee5\u88c5，\u4f46\u662f\u6709\u7684\u65f6\u5019，\u6211\u4eec\u5728\u4f7f\u7528\u65f6，\u60f3\u8981\u9650\u5b9a\u67d0\u4e2a\u74f6\u5b50\u53ea\u80fd\u7528\u6765\u88c5\u4ec0\u4e48，\u8fd9\u6837\u6211\u4eec\u4e0d\u4f1a\u88c5\u9519，\u800c\u7528\u7684\u65f6\u5019\u4e5f\u53ef\u4ee5\u653e\u5fc3\u7684\u4f7f\u7528，\u65e0\u9700\u518d\u4e09\u601d\u91cf\u3002\u6211\u4eec\u751f\u6d3b\u4e2d\u662f\u5728\u4f7f\u7528\u8fd9\u4e2a\u74f6\u5b50\u65f6\u5728\u74f6\u5b50\u4e0a\u201c\u8d34\u6807\u7b7e\u201d，\u8fd9\u6837\u5c31\u8f7b\u677e\u89e3\u51b3\u4e86\u95ee\u9898\u3002<\/p>\n
\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u6cdb\u578b\u662fJDK 5.0\u5f15\u5165\u7684\u7279\u6027，\u5141\u8bb8\u5728\u5b9a\u4e49\u7c7b\u3001\u63a5\u53e3\u6216\u65b9\u6cd5\u65f6\u4f7f\u7528\u7c7b\u578b\u53c2\u6570\u3002\u6cdb\u578b\u7684\u6838\u5fc3\u76ee\u7684\u662f\u63d0\u9ad8\u4ee3\u7801\u590d\u7528\u6027，\u540c\u65f6\u589e\u5f3a\u7c7b\u578b\u5b89\u5168\u6027\u548c\u51cf\u5c11\u5f3a\u5236\u7c7b\u578b\u8f6c\u6362\u7684\u9700\u8981\u3002<\/p>\n
\u4f8b\u5982：java.lang.Comparable\u63a5\u53e3\u548cjava.util.Comparator\u63a5\u53e3，\u662f\u7528\u4e8e\u5bf9\u8c61\u6bd4\u8f83\u5927\u5c0f\u7684\u89c4\u8303\u63a5\u53e3，\u8fd9\u4e24\u4e2a\u63a5\u53e3\u53ea\u662f\u9650\u5b9a\u4e86\u5f53\u4e00\u4e2a\u5bf9\u8c61\u5927\u4e8e\u53e6\u4e00\u4e2a\u5bf9\u8c61\u65f6\u8fd4\u56de\u6b63\u6574\u6570，\u5c0f\u4e8e\u8fd4\u56de\u8d1f\u6574\u6570，\u7b49\u4e8e\u8fd4\u56de0\u3002\u4f46\u662f\u5e76\u4e0d\u786e\u5b9a\u662f\u4ec0\u4e48\u7c7b\u578b\u7684\u5bf9\u8c61\u6bd4\u8f83\u5927\u5c0f，\u4e4b\u524d\u7684\u65f6\u5019\u53ea\u80fd\u7528Object\u7c7b\u578b\u8868\u793a，\u4f7f\u7528\u65f6\u65e2\u9ebb\u70e6\u53c8\u4e0d\u5b89\u5168，\u56e0\u6b64JDK1.5\u5c31\u7ed9\u5b83\u4eec\u589e\u52a0\u4e86\u6cdb\u578b\u3002<\/p>\n
public interface Comparable<T>{ \u00a0 \u00a0 int compareTo(T o) ; }<\/p>\n
public interface Comparator<T>{ \u00a0 \u00a0 \u00a0int compare(T o1, T o2) ; }<\/p>\n
\u5176\u4e2d<T>\u5c31\u662f\u7c7b\u578b\u53c2\u6570，\u5373\u6cdb\u578b\u3002<\/p>\n
public class GenericInterfaceTest {
\n public static void main(String[] args) {
\n Object o = new GenericImpl1().show("2");
\n System.out.println(((String)o).length());\/\/\u5f3a\u8f6c<\/p>\n
\/\/ new GenericImpl2().show("2")\/\/\u62a5\u9519
\n Integer show = new GenericImpl2().show(2);\/\/\u65e0\u9700\u5f3a\u8f6c
\n }
\n}
\ninterface GenericInterface<T>{
\n T show(T t);
\n}
\nclass GenericImpl1 implements GenericInterface{\/\/\u65e0\u9650\u5b9a\u7c7b\u578b
\n @Override
\n public Object show(Object o) {
\n return o;
\n }
\n}
\nclass GenericImpl2 implements GenericInterface<Integer>{\/\/\/\u9650\u5b9a\u7c7b\u578b\u4e3aInteger
\n @Override
\n public Integer show(Integer integer) {
\n return integer;
\n }
\n} <\/p>\n
\u7c7b\u578b\u5b89\u5168：\u7f16\u8bd1\u65f6\u68c0\u67e5\u7c7b\u578b，\u907f\u514d\u8fd0\u884c\u65f6 ClassCastException<\/p>\n<\/li>\n
\u4ee3\u7801\u7b80\u6d01：\u65e0\u9700\u5f3a\u5236\u7c7b\u578b\u8f6c\u6362<\/p>\n<\/li>\n
\u793a\u4f8b\u5bf9\u6bd4：<\/p>\n
\u65e0\u6cdb\u578b：\u9700\u8981 (String) o\u5f3a\u5236\u8f6c\u6362<\/p>\n<\/li>\n
\u6709\u6cdb\u578b：\u76f4\u63a5\u4f7f\u7528 Integer o<\/font>，\u7f16\u8bd1\u5668\u786e\u4fdd\u7c7b\u578b\u6b63\u786e<\/p>\n<\/li>\n<\/ul>\n<\/li>\n<\/ul>\n <T>, <E>，<K,V>\u7b49<\/p>\n<\/td>\n<\/tr>\n \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u3010\u4fee\u9970\u7b26\u3011 class \u7c7b\u540d<\u7c7b\u578b\u53d8\u91cf\u5217\u8868> \u3010extends \u7236\u7c7b\u3011 \u3010implements \u7236\u63a5\u53e3\u4eec\u3011{ \u00a0 \u00a0\u00a0 \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0} \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u3010\u4fee\u9970\u7b26\u3011 interface \u63a5\u53e3\u540d<\u7c7b\u578b\u53d8\u91cf\u5217\u8868> \u3010implements \u7236\u63a5\u53e3\u4eec\u3011{ \u00a0 \u00a0\u00a0 \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0}<\/p>\n \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u4f8b\u5982： \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0public class ArrayList<E> \u00a0 \u00a0 \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0public interface Map<K,V>{ \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 \u00a0 …. \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0}<\/p>\n \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u3010\u4fee\u9970\u7b26\u3011 <\u7c7b\u578b\u53d8\u91cf\u5217\u8868> \u8fd4\u56de\u503c\u7c7b\u578b \u65b9\u6cd5\u540d(\u3010\u5f62\u53c2\u5217\u8868\u3011)\u3010throws \u5f02\u5e38\u5217\u8868\u3011{ \u00a0 \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 \/\/… \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0}<\/p>\n \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u4f8b\u5982：java.util.Arrays\u7c7b\u4e2d\u7684 \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0public static <T> List<T> asList(T… a){ \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 \u00a0 …. \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0}<\/p>\n \u6cdb\u578b\u7c7b\u683c\u5f0f：<\/p>\n \u4fee\u9970\u7b26\u00a0 class\u00a0 \u7c7b\u540d<\u7c7b\u578b> { }<\/p>\n \u6cdb\u578b\u63a5\u53e3\u683c\u5f0f：<\/p>\n \u4fee\u9970\u7b26\u00a0 interface\u00a0 \u63a5\u53e3\u540d<\u7c7b\u578b> { }<\/p>\n \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u81ea\u4eceJDK1.5\u5f15\u5165\u6cdb\u578b\u7684\u6982\u5ff5\u4e4b\u540e，\u5bf9\u4e4b\u524d\u6838\u5fc3\u7c7b\u5e93\u4e2d\u7684API\u505a\u4e86\u5f88\u5927\u7684\u4fee\u6539，\u4f8b\u5982：\u96c6\u5408\u6846\u67b6\u96c6\u4e2d\u7684\u76f8\u5173\u63a5\u53e3\u548c\u7c7b\u3001java.lang.Comparable\u63a5\u53e3\u3001java.util.Comparator\u63a5\u53e3\u3001Class\u7c7b\u7b49\u7b49\u3002<\/p>\n \u4e0b\u9762\u4ee5Collection\u3001ArrayList\u96c6\u5408\u4ee5\u53caIterator\u8fed\u4ee3\u5668\u4e3a\u4f8b\u6f14\u793a，\u6cdb\u578b\u7c7b\u4e0e\u6cdb\u578b\u63a5\u53e3\u7684\u4f7f\u7528\u3002<\/p>\n import java.util.Arrays;<\/p>\n public class TestRectangle { public double getLength() { public void setLength(double length) { public double getWidth() { public void setWidth(double width) { public double area(){ public double perimeter(){ @Override @Override \u683c\u5f0f：<\/p>\n \u4fee\u9970\u7b26\u00a0 <\u7c7b\u578b>\u00a0 \u8fd4\u56de\u503c\u7c7b\u578b\u00a0 \u65b9\u6cd5\u540d(\u7c7b\u578b\u00a0 \u53d8\u91cf\u540d){ }<\/p>\n public class GenericMethodTest { \/** \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0List<Number> list = new ArrayList<Integer>(); \/\/\u7f16\u8bd1\u9519\u8bef：\u6cdb\u578b\u4e0d\u652f\u6301\u591a\u6001<\/p>\n \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u4e3a\u4e86\u8868\u793a\u5404\u79cd\u6cdb\u578bList\u7684\u7236\u7c7b，\u53ef\u4ee5\u4f7f\u7528\u7c7b\u578b\u901a\u914d\u7b26<\/p>\n \u00a0 \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0List<?>：\u8868\u793a\u5143\u7d20\u7c7b\u578b\u672a\u77e5\u7684List，\u5b83\u7684\u5143\u7d20\u53ef\u4ee5\u5339\u914d\u4efb\u4f55\u7684\u7c7b\u578b<\/p>\n \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 \u8fd9\u79cd\u5e26\u901a\u914d\u7b26\u7684List\u4ec5\u8868\u793a\u5b83\u662f\u5404\u79cd\u6cdb\u578bList\u7684\u7236\u7c7b，\u5e76\u4e0d\u80fd\u628a\u5143\u7d20\u6dfb\u52a0\u5230\u5176\u4e2d\u00a0<\/p>\n \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 List<? extends Number>：\u5b83\u8868\u793a\u7684\u7c7b\u578b\u662fNumber\u6216\u8005\u5176\u5b50\u7c7b\u578b\u00a0<\/p>\n \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 List<? super Number>：\u5b83\u8868\u793a\u7684\u7c7b\u578b\u662fNumber\u6216\u8005\u5176\u7236\u7c7b\u578b<\/p>\n \u6848\u4f8b：<\/p>\n public class GenericTest { List<?\u00a0 extends\u00a0 Number> list = new ArrayList<Integer>();<\/p>\n import java.util.ArrayList; public class GenericExtendsTest { \/\/\u8be5\u65b9\u6cd5\u80fd\u63a5\u6536\u7684\u53c2\u6570：Number\u7684\u5b50\u7c7b List<?\u00a0 super\u00a0 Number> list = new ArrayList<Integer>();<\/p>\n import java.util.ArrayList; public class GenericSuperTest { List<Integer> list1 = new ArrayList<>(); \/\/list\u63a5\u6536\u7684\u6570\u636e\u7c7b\u578b（>=Integer） \u200b<\/p>\n \u274c \u57fa\u672c\u4e0d\u80fd\u5199\u5165 （\u53ea\u80fd\u5199null）<\/p>\n<\/td>\n \u200b<\/p>\n 1. \u4ece\u96c6\u5408\u83b7\u53d6\u5143\u7d20\u5904\u7406 2. \u53ea\u8bfb\u64cd\u4f5c 3. \u751f\u4ea7\u6570\u636e\u4f9b\u4f7f\u7528<\/p>\n<\/td>\n \u200b<\/p>\n \u274c \u53ea\u80fd\u8bfb\u53d6\u4e3a Object \u7c7b\u578b<\/p>\n<\/td>\n \u2705 \u53ef\u5199\u5165 T \u53ca\u5176\u5b50\u7c7b<\/p>\n<\/td>\n \u4fee\u9970\u7b26\u00a0 \u8fd4\u56de\u503c\u7c7b\u578b\u00a0 \u65b9\u6cd5\u540d ( \u6570\u636e\u7c7b\u578b…\u00a0 \u53d8\u91cf\u540d){ }<\/p>\n \u6ce8\u610f：<\/p>\n （1）\u8fd9\u91cc\u7684\u53d8\u91cf\u5176\u5b9e\u662f\u4e00\u4e2a\u6570\u7ec4<\/p>\n （2）\u5982\u679c\u4e00\u4e2a\u65b9\u6cd5\u6709\u591a\u4e2a\u53c2\u6570，\u5305\u542b\u53ef\u53d8\u53c2\u6570，\u53ef\u53d8\u53c2\u6570\u8981\u653e\u5728\u6700\u540e<\/p>\n \u6848\u4f8b：<\/p>\n public class ParamTest { public static int sum(int… a) { \/*public static int sum(int… a, int b) { \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 public static List asList(T… a)：\u8fd4\u56de\u7531\u6307\u5b9a\u6570\u7ec4\u652f\u6301\u7684\u56fa\u5b9a\u5927\u5c0f\u7684\u5217\u8868<\/p>\n \u6cdb\u578b\u672c\u8d28：\u7c7b\u578b\u53c2\u6570\u5316，\u5b89\u5168\u53c8\u7075\u6d3b<\/p>\n<\/li>\n \u901a\u914d\u7b26\u539f\u5219：<\/p>\n extends：\u80fd\u53d6\u4e0d\u80fd\u5b58<\/p>\n<\/li>\n super：\u80fd\u5b58\u4e0d\u80fd\u53d6<\/p>\n<\/li>\n <?>：\u53ea\u8bfb\u4e0d\u5199<\/p>\n<\/li>\n<\/ul>\n<\/li>\n \u53ef\u53d8\u53c2\u6570：\u7c7b\u578b\u540e\u52a0…，\u5fc5\u987b\u5728\u6700\u540e<\/p>\n<\/li>\n PECS\u539f\u5219：Producer Extends, Consumer Super<\/p>\n<\/li>\n<\/ul>\n","protected":false},"excerpt":{"rendered":" \u672c\u6587\u8bb2\u8ff0\u6cdb\u578b\u7684\u6982\u5ff5\u3001\u6cdb\u578b\u7684\u5e94\u7528\u573a\u666f，\u8ba9\u6211\u4eec\u66f4\u4e86\u89e3\u6cdb\u578b\u7684\u4f5c\u7528 \u76ee\u5f553\u3001\u6cdb\u578b\u7684\u76f8\u5173\u540d\u8bcd<\/h4>\n
\n\n
\n \u7c7b\u578b\u53d8\u91cf（Type Variables）<\/td>\n \u4ee3\u8868\u672a\u77e5\u7684\u6570\u636e\u7c7b\u578b<\/td>\n \n \n \u53c2\u6570\u5316\u7c7b\u578b（Parameterized Types）<\/td>\n \u5df2\u6307\u5b9a\u7c7b\u578b\u53c2\u6570\u7684\u7c7b\/\u63a5\u53e3<\/td>\n Comparator<String><\/td>\n<\/tr>\n \n \u6cdb\u5316\u7684\u6570\u7ec4\u7c7b\u578b（GenericArrayType）<\/td>\n \u4ee3\u8868\u672a\u77e5\u7684\u6570\u7ec4\u7c7b\u578b<\/td>\n T[ ]<\/td>\n<\/tr>\n \n \u901a\u914d\u7b26\u7c7b\u578b（WildcardType）<\/td>\n \u8868\u793a\u672a\u77e5\u7c7b\u578b<\/td>\n Comparator<?><\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n 4\u3001\u7c7b\u578b\u53d8\u91cf<T>\u7684\u5e94\u7528\u573a\u666f<\/h4>\n
\n
\n
\u4e8c\u3001\u6cdb\u578b\u7684\u5e94\u7528\u573a\u666f<\/h3>\n
1\u3001\u6cdb\u578b\u7c7b\u4e0e\u6cdb\u578b\u63a5\u53e3<\/h4>\n
\n public static void main(String[] args) {
\n Rectangle[] arr = new Rectangle[4];
\n arr[0] = new Rectangle(6,2);
\n arr[1] = new Rectangle(4,3);
\n arr[2] = new Rectangle(12,1);
\n arr[3] = new Rectangle(5,4);
\n System.out.println("\u6392\u5e8f\u4e4b\u524d：");
\n for (Rectangle rectangle : arr) {
\n System.out.println(rectangle);
\n }
\n Arrays.sort(arr);
\n System.out.println("\u6392\u5e8f\u4e4b\u540e：");
\n for (Rectangle rectangle : arr) {
\n System.out.println(rectangle);
\n }
\n }
\n}
\nclass Rectangle implements Comparable<Rectangle>{
\n private double length;
\n private double width;
\n public Rectangle(double length, double width) {
\n this.length = length;
\n this.width = width;
\n }<\/p>\n
\n return length;
\n }<\/p>\n
\n this.length = length;
\n }<\/p>\n
\n return width;
\n }<\/p>\n
\n this.width = width;
\n }<\/p>\n
\n return length * width;
\n }<\/p>\n
\n return 2 * (length + width);
\n }<\/p>\n
\n public String toString() {
\n return "Rectangle{" +
\n "length=" + length +
\n ", width=" + width +
\n ",area =" + area() +
\n ",perimeter = " + perimeter() +
\n '}';
\n }<\/p>\n
\n public int compareTo(Rectangle o) {
\n int compare = Double.compare(area(), o.area());
\n return compare != 0 ? compare : Double.compare(perimeter(),o.perimeter());
\n }
\n}<\/p>\n2\u3001\u6cdb\u578b\u65b9\u6cd5<\/h4>\n
\n public static void main(String[] args) {
\n \/\/\u4e0d\u4f7f\u7528\u6cdb\u578b
\n String[] strArr = {"\u5b59\u884c\u8005","\u8005\u884c\u5b59","\u884c\u8005\u5b59"};
\n Object e = new GenericMenthod().getElementNoGeneric(strArr,2);
\n System.out.println(e);
\n System.out.println(((String)e).length());
\n\/\/ \u4f7f\u7528\u6cdb\u578b
\n Integer[] intArr = {2,6,1};
\n Integer element = new GenericMenthod().getElement(intArr, 1);
\n System.out.println(element);
\n }
\n}
\nclass GenericMenthod{
\n \/**
\n * \u8fd4\u56de\u6307\u5b9a\u7d22\u5f15\u4f4d\u7f6e\u5143\u7d20
\n *\/
\n public Object getElementNoGeneric(Object[] array,int index){
\n return array[index];
\n }<\/p>\n
\n * \u8fd4\u56de\u6307\u5b9a\u7d22\u5f15\u4f4d\u7f6e\u5143\u7d20
\n *\/
\n public <T> T getElement(T[] array,int index){
\n return array[index];
\n }
\n} <\/p>\n3\u3001\u7c7b\u578b\u901a\u914d\u7b26<\/h4>\n
3.1\u3001\u4e3a\u4ec0\u4e48\u9700\u8981\u901a\u914d\u7b26<\/h5>\n
3.2\u3001\u4f5c\u7528<\/h5>\n
3.3\u3001\u7c7b\u578b\u901a\u914d\u7b26\u7684\u5206\u7c7b<\/h5>\n
\n
\n
\n
\n public static void main(String[] args) {
\n System.out.println("———-\u7c7b\u578b\u901a\u914d\u7b26：<?>");
\n List<?> list1 = new ArrayList<Object>();
\n List<?> list2 = new ArrayList<Number>();
\n List<?> list3 = new ArrayList<Integer>();
\n \/\/list1.add(3);\/\/\u7f16\u8bd1\u4e0d\u901a\u8fc7
\n }
\n}<\/p>\n3.4\u3001\u4e0a\u9650\u901a\u914d\u7b26<\/h5>\n
\nimport java.util.List;<\/p>\n
\n public static void main(String[] args) {
\n List<? extends Number> list = new ArrayList<>();
\n\/\/ list.get(1);\/\/\u7f16\u8bd1\u901a\u8fc7
\n\/\/ list.add(1);\/\/\u7f16\u8bd1\u4e0d\u901a\u8fc7，\u6cdb\u578b\u4ee3\u8868\u786e\u5b9a\u7684\u7c7b\u578b，？\u4ee3\u8868\u4e0d\u786e\u5b9a\u7c7b\u578b
\n List<Integer> list1 = new ArrayList<>();
\n list1.add(1);
\n list1.add(2);
\n list1.add(3);
\n printElement(list1);
\n }<\/p>\n
\n private static void printElement(List<? extends Number> list) {
\n for (Number number : list) {
\n System.out.println(number);
\n }
\n }
\n}<\/p>\n3.5\u3001\u4e0b\u9650\u901a\u914d\u7b26<\/h5>\n
\nimport java.util.List;<\/p>\n
\n public static void main(String[] args) {
\n List<? super Integer> list = new ArrayList<>();
\n\/\/ list.add(1);\/\/\u7f16\u8bd1\u901a\u8fc7
\n\/\/ Object object = list.get(1);\/\/\u8bfb\u4e0d\u592a\u597d\u7528<\/p>\n
\n addElement(list1,2);
\n System.out.println(list1);
\n List<? super Integer> list2 = new ArrayList<>();
\n addElement1(list2,2);
\n System.out.println(list2);
\n }<\/p>\n
\n private static void addElement(List<? super Integer> list, Integer e) {
\n list.add(e);
\n }
\n \/\/list\u63a5\u6536\u6570\u636e\u7c7b\u578b（>=T）
\n private static<T> void addElement1(List<? super T> list1, T e) {
\n list1.add(e);
\n }
\n}<\/p>\n\n\n
\n <\/td>\n \u8bfb\u53d6\u80fd\u529b<\/td>\n \u5199\u5165\u80fd\u529b<\/td>\n \u4e3b\u8981\u7528\u9014<\/td>\n \u7c7b\u578b\u5b89\u5168<\/td>\n<\/tr>\n \n \u4e0a\u9650\u901a\u914d\u7b26<? extends T><\/td>\n \u2705 \u53ef\u5b89\u5168\u8bfb\u53d6\u4e3a T \u7c7b\u578b<\/td>\n \n \n \u8bfb\u53d6\u5b89\u5168<\/td>\n<\/tr>\n \n \u4e0b\u9650\u901a\u914d\u7b26<? super T><\/td>\n \n \n 1. \u5411\u96c6\u5408\u6dfb\u52a0\u5143\u7d20 2. \u5199\u5165\u64cd\u4f5c 3. \u6d88\u8d39\u6570\u636e<\/td>\n \u5199\u5165\u5b89\u5168<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n \u4e09\u3001\u53ef\u53d8\u53c2\u6570<\/h3>\n
1\u3001\u683c\u5f0f<\/h4>\n
\n public static void main(String[] args) {
\n System.out.println(sum());
\n System.out.println(sum(10));
\n System.out.println(sum(10, 20));
\n System.out.println(sum(10, 20, 30));
\n System.out.println(sum(10, 20, 30, 40));
\n int[] intArr = {10, 20, 30, 40};
\n System.out.println(sum(intArr));
\n }<\/p>\n
\n int sum = 0;
\n for (int i : a) {
\n sum += i;
\n }
\n return sum;
\n }<\/p>\n
\n return 0;
\n }*\/
\n}<\/p>\n2\u3001\u53ef\u53d8\u53c2\u6570\u7684\u5e94\u7528\u573a\u666f<\/h4>\n
\n
\n\u603b\u7ed3<\/h3>\n
\n
\n
\n\u4e00\u3001\u6cdb\u578b\u7684\u6982\u5ff5
\n1\u3001\u4ec0\u4e48\u662f\u6cdb\u578b
\n2\u3001\u6cdb\u578b\u7684\u597d\u5904
\n3\u3001\u6cdb\u578b\u7684\u76f8\u5173\u540d\u8bcd
\n4\u3001\u7c7b\u578b\u53d8\u91cf\u7684\u5e94\u7528\u573a\u666f\u4e8c\u3001\u6cdb\u578b\u7684\u5e94\u7528\u573a\u666f
\n1\u3001\u6cdb\u578b\u7c7b\u4e0e\u6cdb\u578b\u63a5\u53e3
\n2\u3001\u6cdb\u578b\u65b9\u6cd5
\n3\u3001\u7c7b\u578b\u901a\u914d\u7b26
\n3.1\u3001\u4e3a\u4ec0\u4e48\u9700\u8981\u901a\u914d\u7b26
\n3.2\u3001\u4f5c\u7528
\n3.3\u3001\u7c7b\u578b\u901a\u914d\u7b26\u7684\u5206\u7c7b
\n3.4\u3001\u4e0a\u9650\u901a\u914d\u7b26
\n3.5\u3001\u4e0b\u9650\u901a\u914d\u7b26
\n\u4e09\u3001\u53ef\u53d8\u53c2\u6570
\n1\u3001\u683c\u5f0f
\n2\u3001\u53ef\u53d8\u53c2\u6570\u7684\u5e94\u7528\u573a\u666f
\n\u603b\u7ed3 \u4e00\u3001\u6cdb\u578b\u7684\u6982\u5ff5
\n1\u3001\u4ec0\u4e48\u662f\u6cdb\u578b \u4f8b\u5982&#x<\/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":[99,190],"topic":[],"class_list":["post-64963","post","type-post","status-publish","format-standard","hentry","category-server","tag-java","tag-190"],"yoast_head":"\n