Object类之equals()方法

TestEquals.java

//Object之equals方法
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);//false
		System.out.println(c1.equals(c2));//true，c1.equals使用的是Cat中重写的equals()方法
		
		String s1 = new String("hello");
		String s2 = new String("hello");
		System.out.println(s1 == s2);//false
		System.out.println(s1.equals(s2)); //true，s1.s1.equals使用的是String类中的equals()方法
	}
}

class Cat {
	int color;
	int height, weight;
	
	public Cat(int color, int height, int weight) {
		this.color = color;
		this.height = height;
		this.weight = weight;
	}
	
	//重写的equals()方法
	public boolean equals(Object obj) {
		if(obj == null) return false;
		else {
			if(obj instanceof Cat) {	//instanceof用来判断内存中实际对象A是不是B类型
				Cat c = (Cat)obj;
				if(c.color == this.color && c.height == this.height && c.weight == this.weight) {
					return true;
				}
			}
		}
		
		return false;
	}
	
}