State of Derived class object when Base class constructor calls overridden method in Java

Question

Please refer to the Java code below:

class Base{
     Base(){
         System.out.println(\"Base Constructor\");
         method();
     }
     void method()         


        

Answer 1

Why does the overridden method get called if the Derived class object isn't created yet?

Derived class constructor implicitly calls the Base class constructor as the first statement. Base class constructor calls method() which invokes the overridden implemention in the Derived class because that is the class whose object is being created. method() in Derived class sees var as 0 at that point.

At what point in time is var assigned value 0?

var is assigned the default value for int type i.e. 0 before the contructor of Derived class is invoked. It gets assigned the value of 2 after the implicit superclass contructor call has finished and before the statements in Derived class's constructor start executing.

Are there any use cases where such behavior is desired?

It is generally a bad idea to use non-final non-private methods in the constructors/initializers of a non-final class. The reasons are evident in your code. If the object that is being created is a subclass instance, the methods may give unexpected results.