Java SE入门及基础（29）

第三节访问修饰符

1. 概念

访问修饰符就是控制访问权限的修饰符号

2. 类的访问修饰符

类的访问修饰符只有两种：public 修饰符和默认修饰符（不写修饰符就是默认）

public 修饰符修饰类表示类可以公开访问。默认修饰符修饰类表示该类只能在同一个包中可以访问。

示例

package cn .we . chapter ;

//使用默认修饰符修饰类时，该类只能在同一个包的其他类中使用

class Teacher {

}

package cn .we . chapter ;

public class School {

private Teacher [] teachers ; // 可以访问 Teacher 类

}

package cn .we . chapter . test ;

import cn .we . chapter . Teacher ;

public class TeacherTest {

        public static void main ( String [] args ) {

                Teacher teacher = new Teacher ();

        }

}

3. 类成员访问修饰符

类成员包括了成员属性和成员方法。类成员访问修饰符换言之就是成员属性和成员方法的访问修饰符。

示例

package cn .we . chapter ;

public class School {

        private Teacher [] teachers ; // 可以访问 Teacher 类

                //使用默认修饰符修饰name 属性

String name ;

        protected int age ;

        public String address ;

        public void show (){

               System . out . println ( teachers . length + "\t" + name + "\t" + age + "\t" + address );

         }

}

package cn .we . chapter ;

public class SchoolTest {

        public static void main ( String [] args ) {

                School school = new School ();

                //外部不能访问private 修饰的属性

                System . out . println ( school . teachers );

                System . out . println ( school . name );

                System . out . println ( school . age );

                System . out . println ( school . address );

        }

}

package cn .we . chapter . test ;

import cn . lyxq . chapter11 . School ;

public class SchoolTest1 {

        public static void main ( String [] args ) {

                School school = new School ();

                //外部不能访问private 修饰的属性

                System . out . println ( school . teachers );

                System . out . println ( school . name );

                System . out . println ( school . age );

                System . out . println ( school . address );

        }

}