protected.java

//Father.java
package test;
public class Father {
    protected void hello() {
        System.out.println("hello");
    }
}

//Son.java
package test;
public class Son extends Father {
    public void tellYourFatherSayHello() {
        hello();
    }
}

//StrangerSamePackage.java
package test;
public class StrangerSamePackage {
    public void sayHello() {
        Father f = new Father();
        f.hello();
    }
}

//SonOtherPackage.java
package other;
public class SonOtherPackage extends Father {
    public void tellYourFatherSayHello() {
        hello();
    }
}

//StrangerOtherPackage.java
package other;
public class StrangerOtherPackage {
    public void sayHello() {
        Father f = new Father();
        f.hello(); // COMPILATION ERROR
    }
}