【JAVA】 protected和default访问属性实例

Java中一共有四种访问属性，public、protected、private和default。

看了这个表各种权限就一目了然了，下面针对protected和default给出实例

首先是基类Person

package package1;

public class Person {
	 public Person(String n,int h)
	 {
		 name=n;
		 height=h;
	 }
	protected String name;			
	int height;
	protected String getName()
	{
		return name;
	}
	int getHeight()
	{
		return height;
	}
	

}

然后是两个派生类Student和Teacher，不过Student和Person在同一包，Teacher不在同一个包中。

package package1;

public class Student extends Person{

	public Student(String n,int h,String stuid,int clnum)
	{
		super(n,h);
		studentId=stuid;
		classnumber=clnum;
	}
	protected String getStuId()
	{
		return studentId;
	}
	int getClassnumber()
	{
		return classnumber;
	}
	protected String studentId;
	int classnumber;
	
}

package package2;

import package1.Person;

public class Teacher extends Person{
	protected String teachId;
	String course;
	public Teacher(String n,int h,String tid,String cou)
	{
		super(n,h);
		teachId=tid;
		course=cou;
	}
	public static void main(String[] args) {
		// TODO Auto-generated method stub
		Teacher tea1= new Teacher("Mr.Wang",168,"10001","Math");
		tea1.name="Teacher Wang"; //ok!
		//tea1.height=177			wrong!
		System.out.println(tea1.getName());	//ok!
		//tea1.getHeight();		wrong，because default
		
	}

}

结果自然如上表所述那样。

然后我又实验了继承的继承是否可以访问，根据学生类又派生出本科生类

package package1;

public class Undergraduate extends Student {
	public Undergraduate(String n,int h,String stuid,int clnum,boolean bool) {
		super(n,h,stuid,clnum);
		hasGirlorBoyfriend=bool;
	}
	private boolean hasGirlorBoyfriend;
	public static void main(String[] args) {
		// TODO Auto-generated method stub
		Undergraduate ungra= new Undergraduate("Lary", 178, "10210001", 3, true);
		System.out.println(ungra.getClassnumber());
		System.out.println(ungra.getHeight());
		System.out.println(ungra.getName());
		System.out.println(ungra.getStuId());
	}

}

发现也是可以的，不管子子类是否与父类在一个包内，都可以访问protected，但不在一个包不能访问default属性的。