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java_SWxC74.java

package snake;

import java.awt.Point;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.KeyEvent;
import java.awt.event.KeyListener;
import java.util.ArrayList;
import java.util.Random;
import java.awt.Color;
import java.awt.Graphics;
import java.awt.Point;
import javax.swing.JFrame;
import javax.swing.Timer;
import javax.swing.JPanel;


public class Snake implements ActionListener, KeyListener {
	
	public static int width = 500;
	public static int height = width / 16 * 12;
	
	public JFrame frame;
	public RenderPanel renderPanel;  
	public static Snake snake;
	
	public Timer timer = new Timer(20, this);	// infinite loop & listener;
	public Point head, apple;	
	public ArrayList<Point> snakeParts = new ArrayList<Point>();
	public Random random;
	
	public static final int SPEED = 1, SCALE = 10, LEFT = 0, UP = 1, RIGHT = 2, DOWN = 3;
	public int tick, direction = DOWN;
	public static int tailLength = 0;  // or 1;	
	public int XBOUND, YBOUND;
	public boolean over, pause, keyPressed;
	
	public static void main(String[] args) {
		snake = new Snake();
	}	
  
	/*CONSTRUCTOR*/
	public Snake() {        
		frame = new JFrame("Snake");
		frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
		frame.setSize(width, height);
		frame.setVisible(true);
		frame.setResizable(false);
		frame.setLocationRelativeTo(null);     // centering the screen;
		frame.getContentPane().add(renderPanel = new RenderPanel());
		frame.addKeyListener(this);
		startGame();		
	}
	
	public void startGame() {
		XBOUND = frame.getWidth() / SCALE - 1;   // set a boundary;
		YBOUND = frame.getHeight() / SCALE - 3;
		random = new Random();
		over = false;
		pause = false;
		tick = 0;
		apple = new Point (random.nextInt(XBOUND), random.nextInt(YBOUND));
		snakeParts.clear();
		head = new Point(0, 0);
		snakeParts.add(new Point(head.x, head.y));
		
		timer.start();      // infinite loop of actionPerformed() method;			
		
	}
	
	
	@Override
	public void actionPerformed(ActionEvent event) {
		renderPanel.repaint();
		tick++;

		if (tick % SPEED == 0 && !over && !pause) {
	
          /************************
          	POINT
          *************************/
          	keyPressed = false;
		
			if (snakeParts.size() >= tailLength && !over) {   // over just for display, so that last tail won't be deleted if game over;
				snakeParts.remove(0);
			}
			
			snakeParts.add(new Point(head.x, head.y));
			
			switch (direction) {
				case DOWN :
					if (head.y + 1 < YBOUND && noTailInFront(head.x, head.y + 1)) {  // if there is tail == death;
						head = new Point(head.x, head.y + 1);
					} else {
						over = true;
					}
					break;
				case RIGHT :
					if (head.x + 1 < XBOUND && noTailInFront(head.x + 1, head.y)) {
						head = new Point(head.x + 1, head.y);
					} else {
						over = true;
					}
					break;
				case UP :
					if (head.y - 1 >= 0 && noTailInFront(head.x, head.y - 1)) {
						head = new Point(head.x, head.y - 1);
					} else {
						over = true;
					}
					break;
				case LEFT :
					if (head.x - 1 >= 0 && noTailInFront(head.x - 1, head.y)) {
						head = new Point(head.x - 1, head.y);
					} else {
						over = true;
					}
					break;
			}  // switch direction		
					
			if (head.equals(apple)) {
				snakeParts.add(head);
				tailLength++;
				apple = new Point (random.nextInt(XBOUND), random.nextInt(YBOUND));
			}
			
		}  // end of tick			
	}  // actionPerformed
			


	public boolean noTailInFront (int x, int y) {    
		for (Point point : snakeParts) {
			if (point.equals(new Point(x, y) ) ) {
				return false;
			}
		}
		return true;
	}
	
		
	@Override
	public void keyPressed (KeyEvent key) {
		
		int i = key.getKeyCode();
		/************************
          	POINT
        *************************/
      	if (keyPressed) {     // key can be pressed only once per loop; 
			return;			  // by returning immediately after key is pressed;
		}
		
		if (i == KeyEvent.VK_RIGHT && direction != LEFT) {
			direction = RIGHT;
			keyPressed = true;
		}
		if (i == KeyEvent.VK_LEFT && direction != RIGHT) {
			direction = LEFT;
			keyPressed = true;
		}
		if (i == KeyEvent.VK_UP && direction != DOWN) {
			direction = UP;
			keyPressed = true;
		}
		if (i == KeyEvent.VK_DOWN && direction != UP) {
			direction = DOWN;
			keyPressed = true;
		}	
		
		if (i == KeyEvent.VK_SPACE) {
			if (!over) {
				pause = !pause;
			} else {
				startGame();	
			}
		}	
			

	} // keyPressed
	
	@Override
	public void keyReleased (KeyEvent key) {	}	
	@Override
	public void keyTyped (KeyEvent key) {	}
	
}



/**************************
 	RENDER CLASS
***************************/

public class RenderPanel extends JPanel {
		

	public void paintComponent(Graphics g) {
		Snake snake = Snake.snake;         // ref to same object (snake) of class Snake; (if we create new obj, it will cause infinite loop)
		int length = snake.snakeParts.size();
		
		g.setColor(Color.BLUE);
		g.fillRect(0, 0, this.getWidth(), this.getHeight());    // as panel (class RenderPanel) size;

		for (Point point : snake.snakeParts) {
			
			if (point == snake.snakeParts.get(length - 1)) {	// set head color distinctly from body;		
				g.setColor(Color.YELLOW);
				g.fillRect(point.x * Snake.SCALE, point.y * Snake.SCALE, Snake.SCALE, Snake.SCALE);
			} else {									
				g.setColor(Color.BLACK);
				g.fillRect(point.x * Snake.SCALE, point.y * Snake.SCALE, Snake.SCALE, Snake.SCALE);
			}
			
		}
		
		g.setColor(Color.RED);
		g.fillOval(snake.apple.x * Snake.SCALE, snake.apple.y * Snake.SCALE, Snake.SCALE, Snake.SCALE);
		
		
	}


	
}