How to call the constructor of an Abstract class from another constructor inside the same class (method overloading) [duplicate]

I am extending the API of a class that I am working on and would like to make it backward compatible - so that it doesn't break any existing users of the class. I have created the new functionality by adding a new parameter to the constructor.

So that I don't repeat code (I could copy-paste code from the old constructor into the new) I would like to change the existing constructor to call the new constructor passing 0 as the default for the new parameter but I am getting a compilation error, method call expected.

Is what I am trying to do not possible (method overloading is not supported?) or am missing something?

To help show what I mean, please see the simple example below,

public abstract class AbstractCalculator { int result; // new parameter being added public AbstractCalculator(int a, int b){ result = a + b; } // existing functionality public AbstractCalculator(int a){ //compilation error here - Method call expected AbstractCalculator(a, 0); } } 

public class Calculator extends AbstractCalculator{ public Calculator(int a){ super(a); } public static void main(String args []){ Calculator calc = new Calculator(4); System.out.println(calc.getResult()); } }