Question

I don’t know exactly how to design a project. It’s my first year at my computer science department. I’m still learning a lot of information about Java, such as inheritance, polymorphism, abstract classes, interfaces, and so on. I am really curious about these lectures and I’m willing to learn them well. Actually I’ve not missed any point in these lectures and I got those very well. But nobody teach me how to desing a project and we are supposed to design a decent Java project at the very end of school.

I and my 3 classmates have decided to make a new game. It is played with only one ball and the ball has changeable two colours. Also two players have the same colour with this ball’s colours. When the ball is at one player’s colour, this player will be able to move the ball and try to score to another player’s goal. These are our idea’s basic logic and we can add some new facilities and options for this game. We are so willing to achieve this project. But… although we listen and learn from our lectures, we are really confused about to design this project step-by-step. I’ve just tried to demonstrate our project’s logic. Meanwhile, we are still learning about GUI but we are at the very beginning of GUI. So I want to understand about what kind of ways we have to follow in order to design and make this kind of project. I just want to know about tricks and shortcuts and make the most of our knowledge about class hierachies, abstract classes, superclasses, overriding, etc.(We know everything about this terms but just don’t know how to use them to design a project). If you can indicate even a little info about these, I would be so so so happy and able to change my point of view. And it would facilitate our progress. Thank you!

Answer 1

You might want to have a look at this Java Pong Game – it’s pretty simple and includes some source code that you can study.

More general advice:

• You need some way to display what is happening in the game. Probably the easiest way to display the screen in a very simple game is to use a JPanel and override it’s paintComponent() method to draw the game screen correctly (e.g. draw players at the right x,y locations)
• You will also need a game loop that should do the following things:
  • Reads any input from players
  • Update the positions of the objects in the game
  • call repaint() on the JPanel so that the screen gets redrawn
  • Waits a short amount of time using e.g. Thread.sleep(30) to sleep for 30 milliseconds
  • Loops back to the start of the game loop
• I would recommend separating the classes that define the user interface (frames, panels etc.) from classes that define the game logic (players, balls etc.). Ideally the game logic classes shouldn’t contain any code that relates to how they are displayed or interacted with.

For a game this simple, you don’t actually need many classes. I’d recommend something like:

• App – contains the main(…) function which launches the game. At a minimum it should create a JFrame and add a single GamePanel inside it, but you can create other UI elements if you like. You may choose to implement your game loop also in this class – in which case the main method should call this once all the setup has been done.
• GamePanel (which extends JPanel) – contains the screen drawing logic, also perhaps detects mouse movement
• Game – class that represents the entire state of the game, including the locations of both players and the ball
• Player – small class to represent the player, with x,y co-ordinates
• Ball – small class to represent the ball, with x,y co-ordinates and dx,dy velocity