Java Magazine - May/June 2012

//new to java /

The End of the Game

COMMUNITY

Let’s finish our game and share it with the world.

MICHAEL KÖLLING

The game we continued build- ing in the previous issue of Java Magazine is getting nearer to completion, but some parts are still missing. Today, I’ll show you how to finish the game and—most importantly—how to share it with your friends. If you haven’t been playing along, you can download Greenfoot and our project and join in the fun.

Ending the Game

Currently, there is no way to win this game. Eat all the pizza slices, and nothing happens. No fanfare, no big “YOU WIN!” sign. Equally, when the snakes catch you, the game just quietly runs on.

We want to fix both those situations. Let’s say that when you manage to eat 12 slices of pizza, you win. The game stops, and we hear a victorious fanfare. However, when the snakes catch you, you lose. We get a rather sad losing sound, and the game stops.

The second scenario (losing) is easier to do—we have almost everything for that already. So let’s do that first, and then look at the functionality for winning.

Losing (Being Eaten by Snakes)

We already have a sound effect for when the snake eats the turtle (in the Snake’s eat method), which uses Greenfoot’s playSound method. The first thing we do is just change the sound to a new sound file (which is included with the project download) named trombone.wav.

Then we add a new line: a call to Greenfoot’s stop method to stop the game at this point. Together, the code looks like this: dot), press Ctrl-Space on your keyboard, and you will see a list of all methods that you can call at this point, as shown in Figure 1. Starting to type a method name will narrow the choices. Then choose any of the methods from the list.

JAVA IN ACTION

Figure 1

Greenfoot.playSound ("trombone.wav"); Greenfoot.stop();

ABOUT US PHOTOGRAPH BY JOHN BLYTHE

Note that both methods are static methods of the Greenfoot class, so we have to write the class name Greenfoot and a dot (full stop) before the method name in the method call.

To discover what other methods the Greenfoot class offers, choose Greenfoot Class Documentation from the Help menu.

Alternatively, you can use code completion. For example, after typing Greenfoot. (that is, after the

Winning (Finishing Your Pizza)

We want our winning functionality (fanfare and stopping the game) to occur when we have eaten our whole pizza ( 12 slices).

In choosing this criterion, we have two problems. First, we currently have only 7 slices of pizza in our game. We could, of course, simply put 12 slices in from the start, but that would make the game too easy. Instead, I want to make a new slice appear each time one is eaten.

And secondly, we now need to count how much we have eaten, so we know when to stop. We don’t know how to do that yet.

The Magically Appearing Pizza The pizza slices get eaten in the Turtle class—to be specific, in the turtle’s eat method. So this is where we start to work. To keep the code clean, we will place the instructions to create a new pizza slice in a separate method and call that method from here. So we place a call to placeNewPizza() into our eat method, just below the playing of the sound: