/**
 * A command executed by a view. Subclasses implement
 * the hook method, clients call execute which will
 * call the hook method. Client code can assume
 * every command has an execute method, but the execute
 * method calls the hook method which does the real work.
 */

public abstract class ViewCommand
{
    public void execute(PuzzleView view)
    {
	hook(view,null);
    }
    public void execute(PuzzleView view, Object o)
    {
	hook(view,o);
    }

    protected abstract void hook(PuzzleView view, Object o);
}