java中equals方法的重寫
Object類中定義有:public blooean equals(Object obj)方法,提供定義“物件內容相等”的邏輯。
程式碼小案例
package com.jackfujia.oo2;
public class TestEquals {
public static void main(String[] args) {
Object obj;
String str;
User u1 = new User(1000, "付佳", "123456");
User u2 = new User(1000, "付翊坤", "123456");
System.out.println(u1 == u2);
System.out.println(u1.equals(u2));
String str1 = new String("我是大好人");
String str2 = new String("我是大好人");
//String 類也重寫了equals方法,才能對字元進行比對。
System.out.println(str1 == str2);
System.out.println(str1.equals(str2));
}
}
class User{
int id;
String name;
String pwd;
public User(int id, String name, String pwd) {
super();
this.id = id;
this.name = name;
this.pwd = pwd;
}
//重寫equals方法,讓其只針對id進行比對。
//用alt + shift + s 選擇 Generate hashCode() and equals()...選項自動生成
@Override
public int hashCode() {
final int prime = 31;
int result = 1;
result = prime * result + id;
return result;
}
@Override
public boolean equals(Object obj) {
if (this == obj)
return true;
if (obj == null)
return false;
if (getClass() != obj.getClass())
return false;
User other = (User) obj;
if (id != other.id)
return false;
return true;
}
}