map的使用

package 容器类;import java.util.*;// 所有的用法请参考  Api 文档class Am{private int a;public Am(int a){this.a = a;}public int getA() {return a;}}public class map1 {public static void main(String[] args) {HashMap hm = new HashMap<Integer,Am>();hm.put(1,new Am(5)); //放入映射关系hm.put(2,new Am(5)); Am am = (Am)hm.get(1); //提取映射关系System.out.println(am.getA());System.out.println(hm.containsKey(1)); System.out.println(hm.size());hm.remove(1); // 删除映射关系System.out.println(hm.size());}}