java集合（Map）

import java.util.*;/** * java map集合是key=>value的元素集合 */public class MapTest {public static void main(String[] args){ Map<String, Integer> m1 = new HashMap<String, Integer>(); Map<String, String> m2 = new HashMap<String, String>();  m2.put("xiaogang", "男"); m2.put("xiaoli", "女");     m1.put("wang", 1);     m1.put("li", 2);     m1.put("zhang", 3);          System.out.println(m1.get("zhang"));     m1.put("zhang", 5);//出现重复key,会更新value          System.out.println(m1.get("wang"));     System.out.println(m2.get("xiaoli"));          System.out.println(m1.keySet());//将所有key转为set集合     System.out.println(m1.values());//将所有value转为list}}

运行结果：

31女[li, zhang, wang][2, 5, 1]