import javax.swing.*;

public class MainWindow extends JFrame {

    public MainWindow(){
        setTitle("SNAKE");
        setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
        setSize(360,360);
        setLocation(400,400);
        add(new GameField());
        setVisible(true);
    }
    public static void main(String[] args){
        MainWindow mw = new MainWindow();
    }
}





import javax.swing.*;
import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.KeyAdapter;
import java.awt.event.KeyEvent;
import java.util.Random;

public class GameField extends JPanel implements ActionListener {

    private final int SIZE = 320;
    private final int DOT_SIZE = 16;
    private final int ALL_DOTS = 400;
    private Image dot;
    private Image apple;
    private int appleX;
    private int appleY;
    private int[] x = new int[ALL_DOTS];
    private int[] y = new int[ALL_DOTS];
    private int dots;
    private Timer timer;
    private boolean left = false;
    private boolean right = true;
    private boolean up = false;
    private boolean down = false;
    private boolean inGame = true;

    public GameField(){
        setBackground(Color.BLACK);
        loadImages();
        initGame();
        addKeyListener(new FieldKeyListener());
        setFocusable(true);
    }

    public void initGame(){
        dots = 3;
        for (int i =0;i<dots;i++){
            x[i] = 48 - i*DOT_SIZE;
            y[i] = 48;
        }
        timer = new Timer(150,this);
        timer.start();
        createApple();
    }

    public void createApple(){
        appleX = new Random().nextInt(20)*DOT_SIZE;
        appleY = new Random().nextInt(20)*DOT_SIZE;
    }


    public void loadImages(){
        ImageIcon iia = new ImageIcon("apple.png");
        apple = iia.getImage();
        ImageIcon iib = new ImageIcon("dot.png");
        dot = iib.getImage();
    }

    @Override
    protected void paintComponent(Graphics g) {
        super.paintComponent(g);
        if(inGame){
            g.drawImage(apple,appleX,appleY,this);
            for (int i = 0; i < dots ; i++) {
                g.drawImage(dot,x[i],y[i],this);
            }
        }else{
            String str = "Game Over";
            //Font f = new Font("Arial",14,Font.BOLD);
            g.setColor(Color.white);
           // g.setFont(f);
            g.drawString(str,125,SIZE/2);
        }
    }

    public void move(){
        for (int i = dots; i > 0; i--) {
            x[i] = x[i-1];
            y[i] = y[i-1];
        }
        if(left){
            x[0] -= DOT_SIZE;
        }
        if(right){
            x[0] += DOT_SIZE;
        }
        if(up){
            y[0] -= DOT_SIZE;
        }
        if(down){
            y[0] += DOT_SIZE;
        }
    }

    public void checkApple(){
        if(x[0] == appleX && y[0] == appleY){
            dots++;
            createApple();
        }
    }

    public void checkCollisions(){
        for (int i = dots; i >0 ; i--) {
            if(i>4 && x[0] == x[i] && y[0] == y[i]){
                inGame = false;
            }
        }
        if (x[0]>SIZE){
                inGame = false;
        }
        if (x[0]<0){
            inGame = false;
        }
        if (y[0]>SIZE){
            inGame = false;
        }
        if (y[0]<0){
            inGame = false;
        }
    }

    @Override
    public void actionPerformed(ActionEvent e) {
        if(inGame){
            checkApple();
            checkCollisions();
            move();
        }
        repaint();
    }
class FieldKeyListener extends KeyAdapter{
    @Override
    public void keyPressed(KeyEvent e) {
        super.keyPressed(e);
        int key = e.getKeyCode();
        if(key == KeyEvent.VK_LEFT && !right){
            left = true;
            up = false;
            down = false;
        }
        if(key == KeyEvent.VK_RIGHT && !left){
            right = true;
            up = false;
            down = false;
        }
        if(key == KeyEvent.VK_UP && !down){
            right = false;
            up = true;
            left = false;
        }
        if(key == KeyEvent.VK_DOWN && !up){
            right = false;
            left = false;
            down = true;
        }
    }
}
}