Question

I have a class like this:

public class BaseClass
{
  public BaseClass(URL url, String something, String whatever)
  {
    // Do some stuff with URL, something and whatever
  }

  public List ImportantFunction()
  {
    // Some important stuff here
  }
}

I want to use this class, however I want to do different stuff in the constructor. The things that the constructor does I need to do them differently. But I want to use all the functionality of the other class methods.

I figured the easiest would be to extend the class. However when I do this, the constructor requires me to call the parent constructor:

super(url, something, whatever);

Is it possible to extend the base class but have a completely different constructor? I don’t want the BaseClass constructor to be called at all…

Answer 1

You must invoke a constructor of the superclass. If you don’t explicitly call one, Java will attempt to call the no-argument constructor automatically; if there is no such, you will get a compile error. The constructor you call does not need to correspond to the arguments passed to the subclass’ constructor.

This is mandatory – objects’ member variables can be initialized in a constructor, and not calling one of them could violate the superclass’ internal assumptions.

There is no way around this short of using JNI to break the JVM.