How can a singleton class use an interface?

Question

I read at many places that singletons can use interfaces. Some how I am unable to comprehend this.

Answer 1

Something like:

public interface MyInterface 
{
}

And

public class MySingleton implements MyInterface
{
  private static MyInterface instance = new MySingleton();

  private MySingleton() 
  {
  } 

  public static MyInterface getInstance()
  {
    return instance;
  }
}