Java 访问控制权限

二个包

包：com.pag1

     类：Base

package com.pag1;
public class Base {
    public int a = 1;

    String b = "12";

    protected int c = 1;

    private int d = 4;
    
    public void test(){

        System.out.println(this.getClass()+":"+this.a);
    }

}

     类:  Derived

package com.pag1;
public class Derived extends Base{
    public int a = 2;

    public void  test2(){
        System.out.println(b);
    }
    public static void main(String[] args) {
        new Derived().test2();
    }
}

Derived 能继承Base的除d（private修饰）以外的所有成员变量；

包：com.pag2

package com.pag2;

public class Derived2 extends Base { }

Derived2在和Base不在同一个包，能继承c（protected）和 a（public）修饰的成员变量，不能继承默认和private修饰的成员变量。

public class Base {    public int a = 1;
    String b = "12";
    protected int c = 1;
    private int d = 4;        public void test(){
        System.out.println(this.getClass()+":"+this.a);    }
}