How to call a different constructor conditionally in Java?

Question

Let\'s say someone gives you a class, Super, with the following constructors:

public class Super
{
    public Super();
    public Super(int arg)         


        

Answer 1

Can't be done as such as super must be first statement in a constructor.

The proper alternative is a builder class and to have one constructor in the derived class for each constructor in the super class.

eg.

Derived d = new DerivedBuilder().setArg(1).createInstance();

---

public class DerivedBuilder {

    private int arg;

    // constructor, getters and setters for all needed parameters

    public Derived createInstance() {
        // use appropriate constructor based on parameters
        // calling additional setters if need be
    }
}