[Java] 类的Equals方法 (String, Data类都已经自动重写)

package com.bjsxt.chap03;

public class TestEquals {

    public static void main(String[] args) {
        Cat c1 = new Cat(1, 2, 3);
        Cat c2 = new Cat(1, 2, 3);
        System.out.println(c1 == c2);
        System.out.println(c1.equals(c2));
    
        String s1 = new String("hello");
        String s2 = new String("hello");
        System.out.println(s1 == s2);
        System.out.println(s1.equals(s2));
    }

}
class Cat {
    int color;
    int weight, height;
    public Cat(int color, int weight, int height) {
        this.color = color;
        this.weight = weight;
        this.height = height;
    }
    public boolean equals(Object obj) {
        if (obj == null) {
            return false;
        }
        else {
            if (obj instanceof Cat) {
                Cat c = (Cat)obj;
                if (c.color == this.color && c.height == this.height && c.weight == this.weight) {
                    return true;
                }
            }
        }
        return false;
    }
}

Output

false

true

false

true