深入理解JavaSE的包机制和访问权限控制

package com.xxxx.exam;
public class PackageTest01 {
public static void main(String[] args) {
System.outprintln("Hello Package!!!");
	}
 }

import com.xxxx.exam.model.User;
import com.xxxx.exam.model.Student;
import com.xxxx.exam.model.Employee;

import com.xxxx.exam.model.*;

package com.xxxx.exam;
import java.util.Scanner;
public class PackageTest02 {
public static void main(String[] args) {
	User user = new User();
	Scanner s=new Scanner(System.in);
	int x=s.nextInt();
	user.setUserId(10000);
	user.setUserName("张三");
	System.out.println("user.id=" + user.getUserId());
	System.out.println("user.name=" + user.getUserName());
	}
 }

public class PrivateTest01 {
public static void main(String[] args) {
	A a = new A();
//不能访问，private 声明的变量或方法，只能在同一个类中使用
	System.out.println(a.id);
	} 
}
class A {
	private int id;
}

public class ProtectedTest01 {
public static void main(String[] args) {
		A a = new A();
		a.method1();
		A b = new B();
		b.method1();
		B b1 = new B();
		b1.method3(); 
	}
 }
class A {
//采用 protected 声明的变量或方法只有子类或同一个包下的类可以调用
	protected int id = 100;
	public void method1() {
		System.out.println(id);
	}
	protected void method2() {
		System.out.println("A.method2()");
	}
}
class B extends A {
	public void method1() {
//可以正确调用
//因为和 A在同一个包下
		System.out.println(id);
	}
	public void method3() {
//可以正确调用
	method2();	
	}
 }