Basic Java Examples
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Written by: Dr. Christian A. Duncan

Dr. Duncan now appears to be teaching at Louisiana Tech

Reference: CSC329: Introduction to Game Programming, University of Miami, Spring 2006

TicTacToe

For this task, we have created a simple TicTacToe game. The game has room for two, one, or zero players. In this example, we shall explore the area of making an intelligent computer player and see actually how it can be integrated into this particular game. Here is the relevant code:

TicTacToe Game (to play TicTacToe)
TicTacToe AI System (to have an AI element)

Pong Applet

We have created a very very simple unrefined Pong game, written as an applet. For this lecture, we shall explore some of the details of the game to improve it. In particular, we shall add an AI system to control one of the game's paddles. This task is much more difficult as the AI must work in real-time at the same time that the system is busy handling all the other tasks as well. One approach is to make a thread. Here we get in to Operating Systems programming and we'll see how far we get for this basic issue. But for starters here is the pong applet.

Before we go into some basic details about this particular applet, here are the relevant links:

Pong HTML File (to play Pong)
Pong Java File (the Pong java code)

Details

If you look carefully at the Pong source code, you will see three classes. One deals with the Pong game itself and the other two are for Paddle objects and Ball objects.

The code is somewhat long, about 500+ lines of programs. But, it is designed to be somewhat flexible so adding new features can be easier - sometimes.

Look through the code to get a broad idea of how it works. For example, each Paddle comes equipped with two rectangles: one describes the paddle itself, the other describes its "motion" range. This prevents a paddle from moving outside of its bounds. The reason? To allow more flexible movement while being able to easily define where it can move to.

There are a lot of features so don't try to understand all of it. Look at the method names, descriptions, my limited commenting (sorry), and such to get an idea what is going on. After you have a clear idea of what is happening, think about what you want to do to improve the game.

When it comes to actually implementing changes, you will most likely need features from the AWT package or similar classes. The Pong game currently does use some of these features but by no means does it use all. Refer to the APIs and browsing the documentation to find a method or class that suits your needs. There is a lot there and it is hard to predict exactly what you will need.

Improvements

One thing we would like to do is to improve the game, or create an entirely new game with Pong as the basis.

What I recommend for improvements here is to be creative. Try to change the game as much as possible to do what you like. Here are just a very few suggestions:

Keep track of the score.
Currently, my game just quickly (w/o pause) displays the loser and then terminates. It does not keep track of scoring. Certainly a noble addition. This would also involve displaying the score on the screen somewhere. Maybe at the top? The score can be drawn in the paint method like everything else. Look at how the Pong game displays the "Loser" message using the drawString method.

Allow the Paddles to move left and right as well as up and down.
This involves changing both the keyboard input and how the paddles move.

Allow multiple balls, for a really tough game.

Allow multiple paddles.
These could move in sync with each other or separately with different key commands. For example, you could have three different paddles per player each with commands to move up and down individually.

Place a goal on each side rather than using the whole boundary.
One easy way to do this is to make the "goals" Paddles that don't move. The method hitBall determines if the ball hit the paddle or not. So, you could simply check if the ball hit these "goals" and if so, it would be considered in.

Combine, paddles moving in 4 directions with the goals, and get PongAirHockey.

Combine, multiple paddles with the goals, and get FoosPong.

Redo the keystrokes so they are friendly to use.

Add an AI computer for the second player.
To do this, each iteration in the run() method, the computer adjusts the paddle either up or down (just like entering a key stroke) based on where the ball is located relative to the paddle. It plays a very simple chase game, but it could be written more sophisticated than that.

Change the movement dynamics of the paddles and ball.
Currently, the paddle maintains velocity unless you push the stop key and up or down increases or decreases that velocity. There are many ways to change this. For example, no momentum at all. Pushing down moves up - then stops - continue to hold the key down and it will continue to go up. The ball gets heavy spin based on your speed at the time it hits the paddle. This could be removed or made less significant, by using a fraction of the speed for example.

Keep in mind, that the two players share a keyboard so that when one holds down a key it may not register the other one. One of the reasons, multi-player real-time games don't use keyboards. Networking would get around this but that probably is not the best choice for this assignment... but it could be added!

Add a key to "catch" the ball. If it is pressed when the ball hits the paddle, it sticks and the player can then "shoot" the ball back to the opponent.

Create DodgePong
Each paddle can release a ball if it hits the other paddle, they lose. To prevent bombarding the balls, each paddle may be allowed to release one ball at any time before it hits the opponet of opposite wall. Or maybe the ball bounces back and the player must "catch" their ball again.

Be creative... there are hundreds of little variations that can be done with little effort once the foundation has been written. And the code understood.

Oh, and sorry there is no Pong sound available!