CODEWITHSUNDEEP
javaarraylist
xenerax
xenerax

Reputation: 11

How do I locate a element in my arraylist?

Hi I'm a student and in my class we are programming a litte snake game, now the Problem ist that some times whene an Apple is eaten the game will freez, we figured out that it is propably caused by 2 Apples spawning at the same Position but we don't know how to avoid that. The Apples are generated in an arraylist so I think we need to locate the Elements inside the arraylist to say the Programm it is not allowed to spawn them there and needs to search for a new location until is has found one whithout an existing apple.

I searched on the Internet if there is a solution for my problem but i think it is a bit to specific or I follow the wrong path and some of you will find what I can't.

If you need any more details just write me a message. I'm glad to help you on helping me :D .

private void createApples(int max) {

    int loop = 0;
    int appleX;
    int appleY;
    Element apple;
    boolean exists;
    int index;


    for (loop = 0; loop < max; loop++) {
      exists = false;

      do {
        appleX = 
            new Random().nextInt(bounds.width / SNAKE_SIZE) * 
            SNAKE_SIZE + SNAKE_SIZE / 2;
        appleY =
            new Random().nextInt(bounds.height / SNAKE_SIZE) *
            SNAKE_SIZE + SNAKE_SIZE / 2;

        index = 0;
        while (index < apples.size() && !exists) {
          exists = apples.get(index).equal(appleX, appleY);
          index++;
        }



        if (!exists) 
          exists = player.contains(appleX, appleY);
          exists = player2.contains(appleX, appleY);



      }
      while (exists);

      apple = new Element(appleX, appleY, SNAKE_SIZE, Color.white, bounds);
      apples.add(apple);
    }
  }

Upvotes: 1

Views: 94

Answers (1)

dognose
dognose

Reputation: 20909

Without going through your code in detail: 

if (!exists) 
  exists = player.contains(appleX, appleY);
  exists = player2.contains(appleX, appleY);

without curly braces, you are just applying the condition to the first line here. This is what your computer will see: 

if (!exists){
  exists = player.contains(appleX, appleY);
}

exists = player2.contains(appleX, appleY);

and this means, no matter what you have computed already for exists - it will be overwritten by whatever is true for player2.

But your exists should be true, whenever it is true for player1 OR player2.

You can use the following instead: 

  exists |= player.contains(appleX, appleY);
  exists |= player2.contains(appleX, appleY);

(Shorthand for)

if (!exists) 
   exists = player.contains(appleX, appleY);

if (!exists) 
   exists = player2.contains(appleX, appleY);

Can you add information, what apples is (type), and how your equals / hashcode method on Element is implemented?

while (index < apples.size() && !exists) {
  exists = apples.get(index).equal(appleX, appleY);
  index++;
}

(I guess you implented your own, cause you also called it equal instead of equals)

Upvotes: 2

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