kristofer / SpaceInvadersGame.java

import javax.swing.*; import java.awt.*; 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.List; import java.util.Random; // Read the code, and then explain it! // Do so WITHOUT running it to see what it does. public class SpaceInvadersGame extends JPanel implements KeyListener, ActionListener { private int playerX, playerY; private List<Alien> aliens; private List<Bullet> bullets; private boolean isGameOver; private int score; private SpaceInvadersGame() { playerX = 300; playerY = 480; isGameOver = false; score = 0; aliens = new ArrayList<>(); bullets = new ArrayList<>(); // Initialize aliens for (int i = 0; i < 6; i++) { aliens.add(new Alien(i * 100, 0)); } Timer timer = new Timer(15, this); timer.start(); addKeyListener(this); setFocusable(true); setFocusTraversalKeysEnabled(false); } public void paintComponent(Graphics g) { super.paintComponent(g); // Draw background g.setColor(Color.black); g.fillRect(0, 0, 800, 600); // Draw player g.setColor(Color.blue); g.fillRect(playerX, playerY, 50, 50); // Draw aliens for (Alien alien : aliens) { g.setColor(Color.green); g.fillRect(alien.x, alien.y, 50, 50); } // Draw bullets for (Bullet bullet : bullets) { g.setColor(Color.red); g.fillRect(bullet.x, bullet.y, 10, 20); } // Display score g.setColor(Color.white); g.setFont(new Font("Arial", Font.PLAIN, 20)); g.drawString("Score: " + score, 10, 30); if (isGameOver) { g.setFont(new Font("Arial", Font.PLAIN, 50)); g.drawString("Game Over", 300, 300); } } public void actionPerformed(ActionEvent e) { if (!isGameOver) { // Move aliens for (Alien alien : aliens) { alien.y += 2; } // Move bullets for (Bullet bullet : bullets) { bullet.y -= 5; } // Check for collisions checkCollisions(); // Remove off-screen aliens and bullets aliens.removeIf(alien -> alien.y > 600); bullets.removeIf(bullet -> bullet.y < 0); // Spawn new aliens if (aliens.isEmpty()) { for (int i = 0; i < 6; i++) { aliens.add(new Alien(i * 100, 0)); } } repaint(); } } private void checkCollisions() { for (Alien alien : new ArrayList<>(aliens)) { for (Bullet bullet : new ArrayList<>(bullets)) { if (alien.getBounds().intersects(bullet.getBounds())) { aliens.remove(alien); bullets.remove(bullet); score += 10; } } if (alien.getBounds().intersects(new Rectangle(playerX, playerY, 50, 50))) { isGameOver = true; } } } public void keyTyped(KeyEvent e) {} public void keyPressed(KeyEvent e) { int key = e.getKeyCode(); if (key == KeyEvent.VK_LEFT && playerX > 0) { playerX -= 20; } if (key == KeyEvent.VK_RIGHT && playerX < 750) { playerX += 20; } if (key == KeyEvent.VK_SPACE) { if (!isGameOver) { bullets.add(new Bullet(playerX + 20, playerY)); } else { // Restart the game isGameOver = false; playerX = 300; score = 0; aliens.clear(); bullets.clear(); for (int i = 0; i < 6; i++) { aliens.add(new Alien(i * 100, 0)); } } } } public void keyReleased(KeyEvent e) {} public static void main(String[] args) { JFrame frame = new JFrame("Space Invaders"); SpaceInvadersGame game = new SpaceInvadersGame(); frame.add(game); frame.setSize(800, 600); frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); frame.setVisible(true); } private class Alien { int x, y; Alien(int x, int y) { this.x = x; this.y = y; } Rectangle getBounds() { return new Rectangle(x, y, 50, 50); } } private class Bullet { int x, y; Bullet(int x, int y) { this.x = x; this.y = y; } Rectangle getBounds() { return new Rectangle(x, y, 10, 20); } } }