Java中的间接子类无法访问超类中的受保护成员

Question

Why is it that in Java, a superclass' protected members are inaccessible by an indirect subclass in a different package? I know that a direct subclass in a different package can access the superclass' protected members. I thought any subclass can access its inherited protected members.

EDIT

Sorry novice mistake, subclasses can access an indirect superclasses' protected members.

Answer 1

Perhaps you're a little confused.

Here's my quick demo and shows an indirect subclass accessing a protected attribute:

// A.java
package a;
public class A {
    protected int a;
}

// B.java 
package b;   //<-- intermediate subclass
import a.A;
public class B extends A {
}

// C.java
package c; //<-- different package 
import b.B;
public class C extends B  { // <-- C is an indirect sub class of A 
    void testIt(){
        a++;
        System.out.println( this.a );//<-- Inherited from class A
    }
    public static void main( String [] args ) {
        C c = new C();
        c.testIt();
    }
}

it prints 1

As you see, the attribute a is accessible from subclass C .

If you show us the code you're trying we can figure out where your confusion is.

Answer 2

Maybe the problem is that he try to access the protected field of other instance but not his. such like：

package a;
public class A{
    protected int a;
}

package b;
public class B extends A{

}

package c;
public class C extends B｛
    public void accessField(){
        A ancient = new A();
        ancient.a = 2;  //That wouldn't work.

        a = 2;   //That works.
    }


｝