一、概述

訪問等級比較：public > protected > default > private

無論是方法還是成員變量，這四種訪問權限修飾符作用都一樣

public:不管包外包內，所有類（子類+非子類）均可使用 protected 包內：所有類可使用 包外：子類可使用，非子類不可使用 default 包內：所有類可使用 包外：所有類不可使用 private：僅本類可使用

二、示例代碼

Test包內的父類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包內的子類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包外的子類

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); }}

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