Object之equals方法

默認的equals方法是比較

兩個引用是否指向的是一個對象，兩個對象c1,c2，要驗證 c1==c2 和 c1.equals(c2)是相同的，換湯不換藥

所以要比較其他信息的話，就要自己重寫了

比如在String類中就是重寫了equals類，只要兩個String的字符串相等，且不爲空，就是相等的就是equals返回爲true

public class TestEquals {
	public static void main(String[] args) {
		Cat c1 = new Cat(1,2,3);
		Cat c2 = new Cat(1,2,3);
		Cat c3 = new Cat(2,3,4);
		
		System.out.println(c1 == c2);
		System.out.println(c1.equals(c2));
		System.out.println(c1.equals(c3));
	}
}
class Cat {
	int color;
	int height,weight;
	
	public Cat(int color, int height, int weight) {
		this.color = color;
		this.height = height;
		this.weight = weight;
	}
	public boolean equals(Object obj) {
		if(obj == null) {
			return false;
		}
		else {
			if(obj instanceof Cat) {//判斷是否爲Cat類
				Cat c = (Cat)obj;
				if(c.color == this.color && c.height == this.height &&c.weight == this.weight) {
					return true;
				}
			}
		}
		return false;
	}
}