Question

So I am making a snake game, but if I move from one direction to the other really fast then it says I made a collision with the body and ends the game (for example, if I am going left and I hit down and then left again really fast or down and right really fast, etc.)

I’ve tried a few things already. I changed the way that it checked for a collision by making it a .intersects rather than checking if (x == body[i][0] && y = body[i][1]). I also did a few System.out.println()‘s to see if maybe something was going wrong there. I noticed that sometimes one of the values repeats (either x or y depending on the direction), but I can’t figure out why… I figure that the repeating is why it messes up the collision, but I can’t find the spot where it would be making it repeat.

x and y are being changed by a thread.

Here is the “Drawing” portion of my code. If you need any other snippets of code please let me know.

public void paintComponent(Graphics g) {
    super.paintComponent(g);

    if (numOfFood == 1) {//Checks wether there is food on the GUI
        g.setColor(Color.BLUE);
        g.fillRect(foodX,foodY,12,12);
    }
    else {
        foodX = random.nextInt(103)*12; //Both this and the below line get a random x or y value to put on GUI for food placement
        foodY = random.nextInt(57)*12;

        numOfFood = 1;
    }
    Rectangle headRect = new Rectangle( x, y, 12, 12 ); //Actual rectangle of the head

    Rectangle foodRect = new Rectangle(foodX, foodY, 12, 12); //Food rectangle

    g.setColor(Color.RED);
    g.fillRect(x,y,12,12); //Draws head of Snake
    g.setColor(Color.WHITE);
    g.fillRect(x+2,y+2,8,8); //Draws a white square in the head of the snake

    for (int i = 0; i < n; ++i) { //Collision Checker
        Rectangle bodyRect = new Rectangle(body[i][0],body[i][1],12,12);
        if ( headRect.intersects(bodyRect)) {
            for (int j = 0; j < n; ++j) {
                body[j][0] = -1;
                body[j][1] = -1;
            }
            numOfFood = 1;
            n = 0;
            x = 624;
            y = 348;
            endGame = true;
        }
    }

    g.setColor(Color.RED);
    if (n > 0) { //Puts the snakes body behind the head
        for (int i = 0;i < n; ++i) {
            g.fillRect(body[i][0],body[i][1],12,12);
        }
    }

    for (int i = n-1;i >= 0; --i) { //Inserts the head at the first part of the array so that the body moves
        if (body[i][0] != -1 && body[i][1] != -1) {
            body[i+1][0] = body[i][0];
            body[i+1][1] = body[i][1];
        }

        if (i == 0) {
            body[i][0] = x;
            body[i][1] = y;
        }
    }

    if (headRect.intersects(foodRect)) { //If the food rectangle and the head rectangle intersect then the snake got the food.
      numOfFood = 0;
      n++;
    }
}

Answer 1

When do you call paintComponent? I suspect that you have one method that continuously moves the snake forward in regular intervals, but paintComponent is responsible for making the snake longer.

You should move collision and moving the snake into the same method that is responsible for moving the head in the direction the snake is moving.

Otherwise, paintComponent might be called many times on one move update, and this is responsible for duplicates of x and y in your array.