一、概述

访问等级比较：public > protected > default > private

无论是方法还是成员变量，这四种访问权限修饰符作用都一样

• public:不管包外包内，所有类（子类+非子类）均可使用
• protected
  • 包内：所有类可使用
  • 包外：子类可使用，非子类不可使用
• default
  • 包内：所有类可使用
  • 包外：所有类不可使用
• private：仅本类可使用
  

二、示例代码

Test包内的父类Permission

public class Permission { private int privateValue = 1; public int publicValue = 1; protected int protectedValue = 1; int defaultValue = 1; void defaultFunc(){ System.out.println("This is a default function"); } public void publicFunc(){ System.out.println("This is a public function"); } protected void protectedFunc() { System.out.println("This is a protected function"); } private void privateFunc(){ System.out.println("This is a private function"); }}

Test包内的子类SubPermission

public class SubPermission extends Permission{ public void permissionTest(){ // public, protected, default function and variable can be used System.out.println("this is a default value:" + this.defaultValue); System.out.println("this is a public value:" + this.publicValue); System.out.println("this is a protected value:" + this.protectedValue); this.publicFunc(); this.protectedFunc(); this.defaultFunc(); }}

Test包外的子类

import base.Test.Permission;public class Demo extends Permission { public static void main(String[] args) { // if is not a subclass, only public function and variable can be used Permission obj = new Permission(); obj.publicFunc(); System.out.println("this is a public value:" + obj.publicValue); // if is a subclass, public and protected function and variable can ba used Demo demo = new Demo(); demo.publicFunc(); demo.protectedFunc(); System.out.println("this is a public value:" + demo.publicValue); System.out.println("this is a protected value:" + demo.protectedValue); }}

以上就是本文的全部内容，希望对大家的学习有所帮助，也希望大家多多支持。