【Java每日一题】20170104

package Jan2017;  
import java.util.HashSet;  
import java.util.Set;  
  
public class Ques0104{  
   public static void main(String[] args){  
       Obj obj01 = new Obj("张三");  
       Obj obj02 = new Obj("李四");  
       Obj obj03 = new Obj("李四");  
  
       Set<Obj> set = new HashSet<Obj>();  
       set.add(obj01);   
       set.add(obj02);   
       set.add(obj03);   
       System.out.println(set.size());  
   }  
}  
  
class Obj{  
    private String id;  
    public Obj(String id){  
        this.id = id;  
    }  
  
    @Override  
    public int hashCode(){  
        return 123;  
    }  
  
    @Override  
    public boolean equals(Object obj){  
        if (this == obj){  
            return true;  
        }  
  
        if (obj instanceof Obj && this.id.equals(((Obj) obj).id)){  
            return true;  
        }  
        return false;  
    }  
}