equals函数的作用

 1 class Test{
 2     public static void main(String args []){
 3         User u1 = new User();
 4         User u2 = new User();
 5         User u3 = u1;
 6 
 7         boolean b1 = u1 == u2;
 8         boolean b2 = u1 == u3;
 9         System.out.println(b1);
10         System.out.println(b2);        
11     }
12 }

 1 class User{
 2     String name;
 3     int age;
 4 
 5     public boolean equals(Object obj){ //判断是否指向堆内存同一个对象
 6         if(this == obj){       
 7             return true;
 8         }
 9 
10         boolean b = obj instanceof User;
11         if(b){
12             User u = (User)obj;  
13             if(this.age == u.age && this.name.equals(u.name)){
14                 return true;
15             }
16             else{
17                 return false;
18             }
19         }
20         else{
21             return false;
22         }
23     }
24 }

 1 class Test{
 2     public static void main(String args []){
 3         User u1 = new User();
 4         User u2 = new User();
 5         User u3 = new User();
 6 
 7         u1.name = "zhangsan";
 8         u1.age = 12;
 9 
10         u2.name = "lisi";
11         u2.age = 12;
12 
13         u3.name = "zhangsan";
14         u3.age = 12;
15 
16         System.out.println(u1.equals(u2));    
17         System.out.println(u1.equals(u3));    
18     }
19 }