for-each loop in Java for different objects

Question

i created a pacman game with everything in it but the problem is that the ghosts and their animation require a lot of code.

example:

every ghost needs 3 if statements at the moment that is 20 lines of code per ghost and if i have 3 ghosts in the game that is 3 x 20 = 60 lines of useless coding..

with my php experience i would say.. use a foreach loop or something similar.. but how should i do this in Java? can someone give me an example? the way i do it now is published below:

creating ghost objects;

DrawPacMan ghost1 = new DrawPacMan();
DrawPacMan ghost2 = new DrawPacMan();

and the painting goes like:

int g1x = 0;
boolean g1r = true;
public void paintComponent(Graphics g) {
    super.paintComponent(g);
    // pacman movement
    diameter = 75;   
    pacman.drawPacMan(g, getHorPlaats(), getVerPlaats(), diameter, getView(), Color.yellow);
    // ghosts movement
    if(g1r == true) {
        g1x += ghostSpeed;          
    }       
    if(g1r == false) {          
        g1x -= ghostSpeed;
    }
    if(g1x == 500 || g1x == 0) {
        g1r = !g1r;
    }
    System.out.println(g1r);
    ghost1.drawGhost(g, g1x, 40, diameter, Color.red);
    ghost2.drawGhost(g, 170, 70, diameter, Color.blue);
}

what exactly is the problem you're trying to solve? Too many lines of code? inefficient re-use of code? Extensive time processing the movement of the ghosts? — Yevgeny Simkin
– Yevgeny Simkin, Commented Oct 12, 2012 at 8:29
@Dr.Dredel OP stated his problem quite clearly: it's the code design. — Marko Topolnik
– Marko Topolnik, Commented Oct 12, 2012 at 8:53

Brian Agnew · Accepted Answer · 2012-10-12 11:47:48Z

7

It looks to me like you're not approaching this in a object-oriented fashion. Why not use a collection of ghosts eg. List<Ghost> and define a Ghost object with it's location, colour etc?

This line:

  ghost1.drawGhost(g, g1x, 40, diameter, Color.red);

would then be replace with

  ghost.draw(g);

and you'd iterate through the list, calling draw() for each.

  for(Ghost ghost : ghosts) {
     ghost.draw(g); // pass in the graphics context
  }

Each ghost knows it's location, colour, state etc. and you can create as many as you like:

  List<Ghost> ghosts = new ArrayList<Ghost>();
  for (int i = 0; i < 10; i++) {  
      ghosts.add(new Ghost());
  }

edited Oct 12, 2012 at 11:47

answered Oct 12, 2012 at 8:30

Brian Agnew

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5 Comments

Atul Over a year ago

@OPThis is a better way... Maybe read a little bit about Strategy Pattern

Reshad Over a year ago

Thanks for the example! but how should my list look like? i'm pretty new to Java and I don't know most of the functions yet..

Brian Agnew Over a year ago

@Reshad - see the amended answer above

Reshad Over a year ago

and the for loop of ghost comes into my drawing class or in my panel class?

Reshad Over a year ago

Could you tell me please what method has to placed in what class or place? i have the PacMan class where my code shown above is from and a DrawGhost class. So i've tried to use your way in my PacMan class since i assumed it belongs there but i only get errors..

Marko Topolnik · Accepted Answer · 2012-10-12 09:10:10Z

2

Since you seem to be new to Java and still getting to know the best idioms, I'll advise on something that is not directly an answer to your question, but is so in a more general sense. Your code

if(g1r == true) {
    g1x += ghostSpeed;          
}       
if(g1r == false) {          
    g1x -= ghostSpeed;
}

can be rewritten as just

g1x += ghostSpeed * (g1r? 1 : -1);

A general note: never compare booleans to literal values. b == true is the same as just b and b == false is the same as !b.

This code

if (g1x == 500 || g1x == 0) {
    g1r = !g1r;
}

will probably result in a bug at runtime as you don't precede it with fencing-in code: g1x can easily step over your limits. You should write instead

if (g1x >= 500) { g1x = 500; g1r = false; }
else if (g1x <= 0) { g1x = 0; g1r = true; }

edited Oct 12, 2012 at 9:10

answered Oct 12, 2012 at 8:49

Marko Topolnik

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1 Comment

Reshad Over a year ago

Thanks for the tips! the second one confused me while i was thinking and the code i wrote worked so i did not look back at it.. but this seems much more logic! gonna change it this way :)

Arham · Accepted Answer · 2012-10-12 08:36:52Z

0

Pass the ghost object as another parameter in the same function paintComponent(Graphics g, Ghost gr)
You can make the conditional statements inline, e.g. g1r == true ? g1x += ghostSpeed : g1x -= ghostSpeed

answered Oct 12, 2012 at 8:36

Arham

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