Package-private inheritance

A.java

package a;

public abstract class A {
    abstract void foo();

    public void callFooA() {
        foo();
    }
}

B.java

package b;

import a.A;

public abstract class B extends A {
    void foo() {
        System.out.println("B.foo()");
    }

    public void callFooB() {
        foo();
    }
}

C.java

package a;

import b.B;

public class C extends B {
    void foo() {
        System.out.println("C.foo()");
    }

    public static void main(String[] args) {
        C c = new C();
        c.foo();
        c.callFooA();
        c.callFooB();
    }
}

/* Produces

C.foo()
C.foo()
B.foo()

*/