【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。