Java访问修饰符原理及代码解析

Java访问修饰符原理及代码解析

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nQlESdK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.printlnhttp://("This is a protected function");

}

private void privateFunc(){http://

System.out.println("This is a private function");

}

}

Test包内的子类SubPermission

public class SubPermission extends Permission{

public void permissionTest(){

http:// // 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);

}

}

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