Object的equals比較兩個物件是否相同，沒有重寫時比較的是記憶體地址是否相同（==）。

但我們有時候比較的是兩個物件中的屬性是否相同，

重寫equals:

package cn.sasa.demo1;

public class Person {
	private String name;
	private int age;
	
	public Person(String name, int age) {
		this.name = name;
		this.age = age;
	}
	
	public String getName() {
		return this.name;
	}
	public void setName(String name) {
		this.name = name;
	}
	
	public int getAge() {
		return this.age;
	}
	public void setAge(int age) {
		this.age = age;
	}
	
	//比較age是否相同
	public boolean equals(Object obj) {
		//return this == obj; //比較記憶體地址
		if(obj == null) {
			return false;
		}
		if(this == obj) {
			return true;
		}
		if(obj instanceof Person) {
			Person p = (Person)obj;
			return this.getAge() == p.getAge();
		}
		return false;
	}
}

package cn.sasa.demo1;

public class Test {
	public static void main(String[] args) {
		Person p1 = new Person("sa", 12);
		Person p2 = new Person("sasa", 121);
		//p2 = p1;
		boolean b = p1.equals(p2);
		System.out.println(b);
	}
}