package 容器类; import java.util.*; class A1{ private int a; public A1(int a){ this.a = a; } public int getA1() { return a; } } public class set1 { public static void main(String[] args) { HashSet<Object> hs = new HashSet<Object>(); A1 aa = new A1(0); hs.add(aa); hs.add(aa); hs.add(new A1(5)); hs.add(new A1(5)); hs.add(4); hs.add(4); hs.add("111"); hs.add("111"); Iterator<Object> it = hs.iterator(); while(it.hasNext()){ Object o = (Object)it.next(); if(o instanceof A1) { A1 m = (A1)o; System.out.println(m.getA1()+" yes1"); } if(o instanceof String) { String s = (String)o; System.out.println(s + "yes2"); } if(o instanceof Integer){ Integer i = (Integer)o; System.out.println(i); } } //System.out.println(hs.size()); //if(hs.contains(5)) System.out.println("yes"); } }