import java.util.Map;
import java.util.HashMap;
import java.util.Set;
import java.util.HashSet;
class  HashFail
{
       public static void main(String[] args)
      {
            Map map=new HashMap();
            Key k=new Key(10);
            map.put(k,"value");   //插入一个key:10
            System.out.println(map.get(k)!=null); //这里显然是true
            k.i++;//关键地方,key改变了
       
           System.out.println(map.get(k)!=null);           //?
           System.out.println(map.get(new Key(10))!=null); //?
           System.out.println(map.get(new Key(11))!=null); //?

           for(int i=0;i<20;i++) map.put(new Object(),new Object());
           //这里加一些无用信息,导致rehash过程

           System.out.println(map.get(k)!=null);           //?
           System.out.println(map.get(new Key(10))!=null); //?
           System.out.println(map.get(new Key(11))!=null); //?

            k.i--;//这里把Key改回去了

            System.out.println(map.get(k)!=null);           //?
            System.out.println(map.get(new Key(10))!=null); //?
            System.out.println(map.get(new Key(11))!=null); //?

       }
      static class Key
     {
           int i;
          Key(int i){
              this.i=i;
          }
          public boolean equals(Object obj){
              return i==((Key)obj).i;
         }
         public int hashCode(){return i;}
     };
}