Question

abstract class Basic (){
    public synchronized void basicMethod(String string){
        //Some actions here
    }
}

public class A extends Basic{
    public void aMethod(){
        //Some actions here
    }
}

public class B extends Basic{
    public void bMethod(){
        //Some actions here
    }
}

Basic a = new A();
Basic b = new B();

a.basicMethod(); // acquires lock
b.basicMethod(); //Same lock?

In other words – lock is related to concrete Object or Super class important too?

Answer 1

Different locks. A synchronized instance method synchronizes on the monitor associated with that particular object instance, so each of a and b has its own monitor.

If you had

abstract class Basic (){
    public synchronized void basicMethod(String string){
        //Some actions here
    }
}

public class A extends Basic{
    public synchronized void aMethod(){
        //Some actions here
    }
}

then calls to a.basicMethod() and a.aMethod() would lock the same monitor.