public class a extends b{}--Calling protected Nember function error!!

[robotcrawl]

//:PackagedClass.java
package hellojava.a;

public class PackagedClass{
public PackagedClass(){
System.out.println("hello I am from packagedClass!");
}
protected void aa(){
System.out.print("hello I am from aa()!");
}
}

//:Foreign.java
package hellojava.b;

import hellojava.a.*;

public class Foreign extends PackagedClass{
public Foreign(){
System.out.println("Foreign Constructor!");
}
public static void main(String[] args){
PackagedClass a = new PackagedClass();
a.aa();
}
}

以下是编译错误：
hellojava/b/Foreign.java:11: aa() has protected access in hellojava.a.PackagedClass
a.aa();
^
1 error

why??

[leonzhao]

从hellojava.b包是访问不到hellojava.a包里面的protected方法的。