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Java 父类的公共方法和字段

欢马劈雪

工程师 (已认证)

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父类的公共方法和字段

实例源码：

源代码：

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/*from N o w J a v a . c o m*/

public class AlphaTwo extends Alpha {

public static void main(String[] args) {

Alpha a = new Alpha();

//a.privateMethod();    //illegal

//a.packageMethod();    //illegal

//a.protectedMethod();  //illegal

a.publicMethod(); //legal

//System.out.format("privateVariable:   %2d%n",

//  a.privateVariable);     //illegal

//System.out.format("packageVariable:   %2d%n",

//  a.packageVariable);     //illegal

//System.out.format("protectedVariable: %2d%n",

//  a.protectedVariable);   //illegal

System.out.format("publicVariable:    %2d%n", a.publicVariable); //legal

AlphaTwo a2 = new AlphaTwo();

a2.protectedMethod(); //legal

System.out.format("protectedVariable: %2d%n", a2.protectedVariable); //legal

}

}
/**
时 代 J a v a 公 众 号 - nowjava.com 提供 
**/

class Alpha {

//member variables

private int privateVariable = 1;

int packageVariable = 2; //default access

protected int protectedVariable = 3;

public int publicVariable = 4;

//methods

private void privateMethod() {

System.out.format("privateMethod called%n");

}

void packageMethod() { //default access

System.out.format("packageMethod called%n");

}

protected void protectedMethod() {

System.out.format("protectedMethod called%n");

}

public void publicMethod() {

System.out.format("publicMethod called%n");

}

public static void main(String[] args) {

Alpha a = new Alpha();

a.privateMethod(); //legal

a.packageMethod(); //legal

a.protectedMethod(); //legal

a.publicMethod(); //legal

System.out.format("privateVariable: %2d%n", a.privateVariable); //legal

System.out.format("packageVariable: %2d%n", a.packageVariable); //legal

System.out.format("protectedVariable: %2d%n", a.protectedVariable); //legal

System.out.format("publicVariable: %2d%n", a.publicVariable); //legal

}

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*     notice, this list of conditions and the following disclaimer.

*   - Redistributions in binary form must reproduce the above copyright

*     notice, this list of conditions and the following disclaimer in the

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*   - Neither the name of Oracle or the names of its

*     contributors may be used to endorse or promote products derived

*     from this software without specific prior written permission.

* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS

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编辑于 2020-03-26 09:23:272020-03-26 09:23:27

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