Ball.java

package Pong;

import java.awt.Color;
import java.awt.Graphics;
import java.util.Random;

public class Ball
{

	public int x, y, width = 25, height = 25;

	public int motionX, motionY;

	public Random random;

	private Pong pong;

	public int amountOfHits;

	public Ball(Pong pong)
	{
		this.pong = pong;

		this.random = new Random();

		spawn();
	}

	public void update(Paddle paddle1, Paddle paddle2)
	{
		int speed = 5;

		this.x += motionX * speed;
		this.y += motionY * speed;

		if (this.y + height - motionY > pong.height || this.y + motionY < 0)
		{
			if (this.motionY < 0)
			{
				this.y = 0;
				this.motionY = random.nextInt(4);

				if (motionY == 0)
				{
					motionY = 1;
				}
			}
			else
			{
				this.motionY = -random.nextInt(4);
				this.y = pong.height - height;

				if (motionY == 0)
				{
					motionY = -1;
				}
			}
		}

		if (checkCollision(paddle1) == 1)
		{
			this.motionX = 1 + (amountOfHits / 5);
			this.motionY = -2 + random.nextInt(4);

			if (motionY == 0)
			{
				motionY = 1;
			}

			amountOfHits++;
		}
		else if (checkCollision(paddle2) == 1)
		{
			this.motionX = -1 - (amountOfHits / 5);
			this.motionY = -2 + random.nextInt(4);

			if (motionY == 0)
			{
				motionY = 1;
			}

			amountOfHits++;
		}

		if (checkCollision(paddle1) == 2)
		{
			paddle2.score++;
			spawn();
		}
		else if (checkCollision(paddle2) == 2)
		{
			paddle1.score++;
			spawn();
		}
	}

	public void spawn()
	{
		this.amountOfHits = 0;
		this.x = pong.width / 2 - this.width / 2;
		this.y = pong.height / 2 - this.height / 2;

		this.motionY = -2 + random.nextInt(4);

		if (motionY == 0)
		{
			motionY = 1;
		}

		if (random.nextBoolean())
		{
			motionX = 1;
		}
		else
		{
			motionX = -1;
		}
	}

	public int checkCollision(Paddle paddle)
	{
		if (this.x < paddle.x + paddle.width && this.x + width > paddle.x && this.y < paddle.y + paddle.height && this.y + height > paddle.y)
		{
			return 1; //bounce
		}
		else if ((paddle.x > x && paddle.paddleNumber == 1) || (paddle.x < x - width && paddle.paddleNumber == 2))
		{
			return 2; //score
		}

		return 0; //nothing
	}

	public void render(Graphics g)
	{
		g.setColor(Color.WHITE);
		g.fillOval(x, y, width, height);
	}

}

Paddle.java

package Pong;

import java.awt.Color;
import java.awt.Graphics;

public class Paddle
{

	public int paddleNumber;

	public int x, y, width = 50, height = 250;

	public int score;

	public Paddle(Pong pong, int paddleNumber)
	{
		this.paddleNumber = paddleNumber;

		if (paddleNumber == 1)
		{
			this.x = 0;
		}

		if (paddleNumber == 2)
		{
			this.x = pong.width - width;
		}

		this.y = pong.height / 2 - this.height / 2;
	}

	public void render(Graphics g)
	{
		g.setColor(Color.WHITE);
		g.fillRect(x, y, width, height);
	}

	public void move(boolean up)
	{
		int speed = 15;

		if (up)
		{
			if (y - speed > 0)
			{
				y -= speed;
			}
			else
			{
				y = 0;
			}
		}
		else
		{
			if (y + height + speed < Pong.pong.height)
			{
				y += speed;
			}
			else
			{
				y = Pong.pong.height - height;
			}
		}
	}

}

Pong.java

package Pong;

import java.awt.BasicStroke;
import java.awt.Color;
import java.awt.Font;
import java.awt.Graphics2D;
import java.awt.RenderingHints;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.KeyEvent;
import java.awt.event.KeyListener;
import java.util.Random;

import javax.swing.JFrame;
import javax.swing.Timer;

public class Pong implements ActionListener, KeyListener
{

	public static Pong pong;

	public int width = 700, height = 700;

	public Renderer renderer;

	public Paddle player1;

	public Paddle player2;

	public Ball ball;

	public boolean bot = false, selectingDifficulty;

	public boolean w, s, up, down;

	public int gameStatus = 0, scoreLimit = 7, playerWon; //0 = Menu, 1 = Paused, 2 = Playing, 3 = Over

	public int botDifficulty, botMoves, botCooldown = 0;

	public Random random;

	public JFrame jframe;

	public Pong()
	{
		Timer timer = new Timer(20, this);
		random = new Random();

		jframe = new JFrame("Pong");

		renderer = new Renderer();

		jframe.setSize(width + 15, height + 35);
		jframe.setVisible(true);
		jframe.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
		jframe.add(renderer);
		jframe.addKeyListener(this);

		timer.start();
	}

	public void start()
	{
		gameStatus = 2;
		player1 = new Paddle(this, 1);
		player2 = new Paddle(this, 2);
		ball = new Ball(this);
	}

	public void update()
	{
		if (player1.score >= scoreLimit)
		{
			playerWon = 1;
			gameStatus = 3;
		}

		if (player2.score >= scoreLimit)
		{
			gameStatus = 3;
			playerWon = 2;
		}

		if (w)
		{
			player1.move(true);
		}
		if (s)
		{
			player1.move(false);
		}

		if (!bot)
		{
			if (up)
			{
				player2.move(true);
			}
			if (down)
			{
				player2.move(false);
			}
		}
		else
		{
			if (botCooldown > 0)
			{
				botCooldown--;

				if (botCooldown == 0)
				{
					botMoves = 0;
				}
			}

			if (botMoves < 10)
			{
				if (player2.y + player2.height / 2 < ball.y)
				{
					player2.move(false);
					botMoves++;
				}

				if (player2.y + player2.height / 2 > ball.y)
				{
					player2.move(true);
					botMoves++;
				}

				if (botDifficulty == 0)
				{
					botCooldown = 20;
				}
				if (botDifficulty == 1)
				{
					botCooldown = 15;
				}
				if (botDifficulty == 2)
				{
					botCooldown = 10;
				}
			}
		}

		ball.update(player1, player2);
	}

	public void render(Graphics2D g)
	{
		g.setColor(Color.BLACK);
		g.fillRect(0, 0, width, height);
		g.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);

		if (gameStatus == 0)
		{
			g.setColor(Color.WHITE);
			g.setFont(new Font("Arial", 1, 50));

			g.drawString("PONG", width / 2 - 75, 50);

			if (!selectingDifficulty)
			{
				g.setFont(new Font("Arial", 1, 30));

				g.drawString("Press Space to Play", width / 2 - 150, height / 2 - 25);
				g.drawString("Press Shift to Play with Bot", width / 2 - 200, height / 2 + 25);
				g.drawString("<< Score Limit: " + scoreLimit + " >>", width / 2 - 150, height / 2 + 75);
			}
		}

		if (selectingDifficulty)
		{
			String string = botDifficulty == 0 ? "Easy" : (botDifficulty == 1 ? "Medium" : "Hard");

			g.setFont(new Font("Arial", 1, 30));

			g.drawString("<< Bot Difficulty: " + string + " >>", width / 2 - 180, height / 2 - 25);
			g.drawString("Press Space to Play", width / 2 - 150, height / 2 + 25);
		}

		if (gameStatus == 1)
		{
			g.setColor(Color.WHITE);
			g.setFont(new Font("Arial", 1, 50));
			g.drawString("PAUSED", width / 2 - 103, height / 2 - 25);
		}

		if (gameStatus == 1 || gameStatus == 2)
		{
			g.setColor(Color.WHITE);

			g.setStroke(new BasicStroke(5f));

			g.drawLine(width / 2, 0, width / 2, height);

			g.setStroke(new BasicStroke(2f));

			g.drawOval(width / 2 - 150, height / 2 - 150, 300, 300);

			g.setFont(new Font("Arial", 1, 50));

			g.drawString(String.valueOf(player1.score), width / 2 - 90, 50);
			g.drawString(String.valueOf(player2.score), width / 2 + 65, 50);

			player1.render(g);
			player2.render(g);
			ball.render(g);
		}

		if (gameStatus == 3)
		{
			g.setColor(Color.WHITE);
			g.setFont(new Font("Arial", 1, 50));

			g.drawString("PONG", width / 2 - 75, 50);

			if (bot && playerWon == 2)
			{
				g.drawString("The Bot Wins!", width / 2 - 170, 200);
			}
			else
			{
				g.drawString("Player " + playerWon + " Wins!", width / 2 - 165, 200);
			}

			g.setFont(new Font("Arial", 1, 30));

			g.drawString("Press Space to Play Again", width / 2 - 185, height / 2 - 25);
			g.drawString("Press ESC for Menu", width / 2 - 140, height / 2 + 25);
		}
	}

	@Override
	public void actionPerformed(ActionEvent e)
	{
		if (gameStatus == 2)
		{
			update();
		}

		renderer.repaint();
	}

	public static void main(String[] args)
	{
		pong = new Pong();
	}

	@Override
	public void keyPressed(KeyEvent e)
	{
		int id = e.getKeyCode();

		if (id == KeyEvent.VK_W)
		{
			w = true;
		}
		else if (id == KeyEvent.VK_S)
		{
			s = true;
		}
		else if (id == KeyEvent.VK_UP)
		{
			up = true;
		}
		else if (id == KeyEvent.VK_DOWN)
		{
			down = true;
		}
		else if (id == KeyEvent.VK_RIGHT)
		{
			if (selectingDifficulty)
			{
				if (botDifficulty < 2)
				{
					botDifficulty++;
				}
				else
				{
					botDifficulty = 0;
				}
			}
			else if (gameStatus == 0)
			{
				scoreLimit++;
			}
		}
		else if (id == KeyEvent.VK_LEFT)
		{
			if (selectingDifficulty)
			{
				if (botDifficulty > 0)
				{
					botDifficulty--;
				}
				else
				{
					botDifficulty = 2;
				}
			}
			else if (gameStatus == 0 && scoreLimit > 1)
			{
				scoreLimit--;
			}
		}
		else if (id == KeyEvent.VK_ESCAPE && (gameStatus == 2 || gameStatus == 3))
		{
			gameStatus = 0;
		}
		else if (id == KeyEvent.VK_SHIFT && gameStatus == 0)
		{
			bot = true;
			selectingDifficulty = true;
		}
		else if (id == KeyEvent.VK_SPACE)
		{
			if (gameStatus == 0 || gameStatus == 3)
			{
				if (!selectingDifficulty)
				{
					bot = false;
				}
				else
				{
					selectingDifficulty = false;
				}

				start();
			}
			else if (gameStatus == 1)
			{
				gameStatus = 2;
			}
			else if (gameStatus == 2)
			{
				gameStatus = 1;
			}
		}
	}

	@Override
	public void keyReleased(KeyEvent e)
	{
		int id = e.getKeyCode();

		if (id == KeyEvent.VK_W)
		{
			w = false;
		}
		else if (id == KeyEvent.VK_S)
		{
			s = false;
		}
		else if (id == KeyEvent.VK_UP)
		{
			up = false;
		}
		else if (id == KeyEvent.VK_DOWN)
		{
			down = false;
		}
	}

	@Override
	public void keyTyped(KeyEvent e)
	{

	}
}

Renderer.java

package Pong;

import java.awt.Graphics;
import java.awt.Graphics2D;

import javax.swing.JPanel;

public class Renderer extends JPanel
{

	private static final long serialVersionUID = 1L;

	@Override
	protected void paintComponent(Graphics g)
	{
		super.paintComponent(g);

		Pong.pong.render((Graphics2D) g);
	}

}