父类的公共方法和字段

/*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

    }

}