[Java知识库]Java的四种不同的权限

对于class的权限修饰符只可以用public和default(缺省)
public类可以在任意地方被访问
default类只可以被同一包内部的类访问

包：com.pan
类：Order.java

package com.pan;
public class Order {
    private int orderPrivate;
    int orderDefault;
    public int orderPublic;
    protected int orderProtected;
    private void methodPrivate() {
        orderPrivate = 1;
        orderDefault = 2;
        orderProtected = 3;
        orderPublic = 4;
    }
    void methodDefault(){
        orderPrivate = 1;
        orderDefault = 2;
        orderProtected = 3;
        orderPublic = 4;
    }
    protected void methodProtected(){
        orderPrivate = 1;
        orderDefault = 2;
        orderProtected = 3;
        orderPublic = 4;
    }
    public void methodPublic(){
        orderPrivate = 1;
        orderDefault = 2;
        orderProtected = 3;
        orderPublic = 4;
    }
}

包：com.pan
类：OrderTest.java

package com.pan;

public class OrderTest {
    public static void main(String[] args) {
        Order order = new Order();
        order.orderDefault = 1;
        order.orderProtected = 2;
        order.orderProtected = 3;

        order.methodPublic();
        order.methodDefault();
        order.methodProtected();

        //同一个包中的其他类，不可以调用Order类中的私有属性和方法
        /*order.orderPrivate = 4;
        order.methodPrivate();*/
    }
}

包：com.hai
类：SubOrder.java

package com.hai;

import com.pan.Order;
//不同包子类
public class SubOrder extends Order {
    public void method(){
        orderPublic = 1;
        orderProtected = 2;

        methodPublic();
        methodProtected();

        //在不同包子类中，不能调用Order类中声明为private和缺省权限的属性和方法
        /*orderDefault = 3;
        orderPrivate = 4;
        methodPrivate();
        methodDefault();*/
    }
}

包：com.hai
类：OrderTest.java

package com.hai;
import com.pan.Order;
//不同包中（同一个工程）
public class OrderTest {
    public static void main(String[] args) {
        Order order = new Order();
        order.orderPublic = 1;
        order.methodPublic();

        //不同包下的普通类（非子类）要使用Order类，不可以调用声明为private，缺省，protected权限的属性，方法
       /* orderProtected = 2;
        orderDefault = 3;
        orderPrivate = 4;
        methodProtected();
        methodPrivate();
        methodDefault();*/
    }
}

关注博主即可阅读全文