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Thread: [Help] Snake algorithm

  1. #1
    Junior Member
    Join Date
    Jul 2011
    Thanked 0 Times in 0 Posts

    Default [Help] Snake algorithm

    I've been making a snake game, and everything works, tho the algorythm of the snake movement isnt that good, but its fine.
    Now, I also have an apple on the screen, and the problem is i can't figure out a way to find if the snakes head & the apple have even 1 common point.

    this is the code of the screen & apple:

     * To change this template, choose Tools | Templates
     * and open the template in the editor.
    package Snake;
    import Tools.ThreadTool;
    import java.awt.*;
    import java.awt.event.KeyEvent;
    import java.awt.event.KeyListener;
    import java.util.*;
    import javax.swing.*;
     * @author User
    public class Screen extends JFrame implements Runnable,KeyListener{
    private int difficulty;    
    private int direction; //0-up 1- down 2-left 3- right
    private Thread t;
    private ArrayList<Integer> snakeX,snakeY;
    private panel panel;
    private int w,h;
    private Apple apple;
        public Screen(int difficulty,int sW,int sH){
            this.difficulty = difficulty;
            this.setSize(sW, sH);
            snakeX = new ArrayList<Integer>();
            snakeY = new ArrayList<Integer>();
            //set width and height of snake
            w = sW/40;
            //add head
            direction = (int)(Math.random()*4);
            apple = new Apple(this, w, h);
            panel = new panel();
            panel.setBackground(new Color(0, 153, 51)); //dark green
        public void run() {
            while(isAlive()){ // change to alive
                    for(int i=snakeX.size();i>1 && snakeX.size() == snakeY.size();i--){
                        snakeX.set(i-1, snakeX.get(i-2));
                        snakeY.set(i-1, snakeY.get(i-2));
                        snakeY.set(0, snakeY.get(0)-h);
                        if(/*snakeX.get(0) == apple.getX() && */snakeY.get(0) == apple.getY())
                    else if(direction==1)
                        snakeY.set(0, snakeY.get(0)+h);
                    else if(direction==2)
                            snakeX.set(0, snakeX.get(0)-w);
                    else if(direction==3)
                        snakeX.set(0, snakeX.get(0)+w);
                ThreadTool.sleep(t, 300/(difficulty+1));
        public void startThread(){
            t = new Thread(this);
        private boolean isAlive(){
            return snakeX.get(0)>=0 && snakeX.get(0)+w<=this.getWidth() && snakeY.get(0)>=0 && snakeY.get(0)+h<=this.getHeight();
        public void keyTyped(KeyEvent e) {
        public void keyPressed(KeyEvent e) {
            if(e.getKeyCode()==KeyEvent.VK_RIGHT && direction != 2)
            else if(e.getKeyCode()==KeyEvent.VK_LEFT && direction !=3)
                direction = 2;
            else if(e.getKeyCode()==KeyEvent.VK_UP && direction!=1)
            else if(e.getKeyCode()==KeyEvent.VK_DOWN && direction!=0)
                direction = 1;
        public void keyReleased(KeyEvent e) {
        class panel extends JPanel{
            public void paintComponent(Graphics g){
                for(int i=0;i<snakeX.size() && snakeX.size() == snakeY.size();i++){
                    g.fillRect(snakeX.get(i), snakeY.get(i), w, h);
                    g.drawRect(snakeX.get(i), snakeY.get(i), w, h);
                    System.err.println("painting at " + snakeX.get(i) + ", " + snakeY.get(i)+","+i);

     * To change this template, choose Tools | Templates
     * and open the template in the editor.
    package Snake;
    import java.awt.Color;
    import java.awt.Graphics;
     * @author User
    public class Apple {
    private Screen screen;
    private int x,y;
    private int w,h;
        public Apple(Screen screen,int w,int h){
            this.screen = screen;
            this.w = w;
            this.h = h;
        public void generateApple(){
            x = (int)(Math.random()*( (screen.getWidth() - w) - 0 + 1) + 0);
            y=(int)(Math.random()*( ( screen.getHeight() - h) - 0 + 1) + 0);
        public void drawMe(Graphics g){
            g.fillRect(x, y, w, h);
            g.drawRect(x, y, w, h);
        public int getX(){
            return x;
        public int getY(){
            return y;

  2. #2
    Forum VIP
    Join Date
    Jul 2010
    Thanked 329 Times in 305 Posts

    Default Re: [Help] Snake algorithm

    Considering that Apple is just a rectangle, I would suggest you revise your Apple class to extend the Rectangle class (Rectangle (Java Platform SE 6)). The Graphics2D class then has 2 methods, one called draw(Shape), and another called fill(Shape). Rectangle implements the Shape Interface, and since Apple would extend Rectangle, you can send either of those two methods an Apple Object. Then, since Apple extends Rectangle, you can call one of its 4 contains() methods on Apple and send it the coordinates (or Point) of the snake's head. Those methods would return a boolean, indicating that the snake's head is somewhere inside the bounds of the Apple.

    Alternatively, you could not extend the Rectangle class and instead write your own contains() method inside your Apple class that accepts an X and Y as its arguments and returns a boolean. The bounds of your Apple is x to x+w and y to y+h (according to the drawRect() method of the Graphics class). If X is between (or equal to) x and x+w AND Y is between (or equal to) y and y+h, the method would return true. Otherwise, it would return false.

    When asking for help, please follow these guidelines to receive better and more prompt help:
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