Thread: Frequent Interview qn

Define your terms. What is a static class? What is a singleton?

Singletons allow you the all the benefits of using object oriented programming (inheritance, polymorphism, etc.). This lets you re-use much of the existing code base.

ex.: A class which counts how many times an ActionEvent is dispatched from various components (doesn't have to be a Singleton, but just pretend it is ).

public class ActionCounter implements ActionListener
{
    private int counter = 0;
 
    public static ActionCounter INSTANCE = new ActionCounter();
 
    private ActionCounter()
    {}
 
    public synchronized void actionPerformed(ActionEvent e)
    {
        ++counter;
    }
 
    public int getCounter()
    {
        return counter;
    }
}

The two different patterns simply allow you to think about your code from a different mind set.