Board.java

package com.codef0x.snake;

import javax.swing.*;
import java.awt.*;
import java.awt.event.KeyEvent;
import java.awt.event.KeyListener;
import java.util.ArrayList;
import java.util.Timer;
import java.util.TimerTask;


public class Board extends JPanel implements KeyListener {
    Snake player;
    Food food;
    ArrayList<SnakePart> snakeCoordinates;

    public Board() {

        this.snakeCoordinates = new ArrayList<>();

        snakeCoordinates.add(new SnakePart(150, 150));
        snakeCoordinates.add(new SnakePart(140, 150));
        snakeCoordinates.add(new SnakePart(130, 150));
        snakeCoordinates.add(new SnakePart(120, 150));

        this.player = new Snake(snakeCoordinates);

        this.food = new Food();
    }

    public static void main(String[] args) {

        JFrame frame = new JFrame("Snake");
        frame.setDefaultCloseOperation(3);

        Board board = new Board();
        frame.add(board);
        frame.setSize(500, 500);
        frame.addKeyListener(new Board());
        frame.setVisible(true);

        board.run(board);
    }

    @Override
    public void paintComponent(Graphics g) {
        clear(g);

        this.player.coordinates.forEach(snakePart -> {
            g.setColor(Color.BLUE);
            g.fillRect(snakePart.x, snakePart.y, 10, 10);
        });

        g.setColor(Color.RED);
        g.fillRect(this.food.foodX, this.food.foodY, 10, 10);

        if (ateFood(this.food, g)) {
            this.food.spawn(getHeight(), getWidth());
            //this.player.grow();
        }
    }

    public void clear(Graphics g) {
        g.clearRect(0, 0, getHeight(), getWidth());
    }

    @Override
    public void update(Graphics g) {
        paintComponent(g);
    }

    public boolean ateFood(Food food, Graphics g) {

        if (this.player.coordinates.get(0).x == food.foodX && this.player.coordinates.get(0).y == food.foodY) {
            g.clearRect(food.foodX, food.foodY, 10, 10);
            return true;
        }
        return false;
    }

    public boolean hitSomething() {
        boolean hitLeftWall = this.player.coordinates.get(0).x < 10;
        boolean hitUpperWall = this.player.coordinates.get(0).y < 0;
        boolean hitRightWall = this.player.coordinates.get(0).x > getWidth() - 10;
        boolean hitLowerWall = this.player.coordinates.get(0).y > getHeight() - 10;

        for (int i = 1; i < 3; i++) {
            if (this.player.coordinates.get(i).x == this.player.coordinates.get(0).x && this.player.coordinates.get(i).y == this.player.coordinates.get(0).y) {
                return true;
            }
        }

        if (hitLeftWall || hitUpperWall || hitRightWall || hitLowerWall) {
            return true;
        }

        return false;
    }

    public void gameOver(Graphics g) {
        clear(g);

        g.setColor(Color.BLACK);
        g.setFont(new Font("TimesRoman", Font.PLAIN, 32));
        g.drawString("Game over!", getWidth() / 2 - 70, getHeight() / 2);
    }

    @Override
    public void keyPressed(KeyEvent event) {
        int keyCode = event.getKeyCode();

        System.out.println("Before altering:");
        System.out.println(player.dx + "  " + player.dy);

        if (keyCode == 37) {
            this.player.dx = -10;
            this.player.dy = 0;
        } else if (keyCode == 38) {
            this.player.dx = 0;
            this.player.dy = -10;
        } else if (keyCode == 39) {
            this.player.dx = 10;
            this.player.dy = 0;
        } else if (keyCode == 40) {
            this.player.dx = 0;
            this.player.dy = 10;
        }

        System.out.println("After altering:");
        System.out.println(player.dx + " "  + player.dy);
    }

    @Override
    public void keyTyped(KeyEvent event) {
        return;
    }

    @Override
    public void keyReleased(KeyEvent event) {
        return;
    }

    public void run(Board board) {
        Timer game = new Timer();
        game.schedule(new TimerTask() {
            boolean initiallySpawned = false;
            @Override
            public void run() {
                Graphics g = board.getGraphics();

                if (hitSomething()) {
                    game.cancel();
                    gameOver(g);
                    return;
                }

                if (!initiallySpawned) {
                    board.food.spawn(getHeight(), getWidth());
                    initiallySpawned = true;
                }

                player.move();

                if (ateFood(food, g)) {
                    food.spawn(getHeight(), getWidth());
                }

                update(g);
            }
        }, 0, 500);
    }
}