用Java写一个多线程小球碰撞程序

好的，以下是一个简单的多线程小球碰撞程序的 Java 代码示例：

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

public class BallCollision extends JPanel implements ActionListener {
    
    private static final long serialVersionUID = 1L;
    private static final int WIDTH = 600;
    private static final int HEIGHT = 400;
    private static final int DELAY = 10;
    private ArrayList<Ball> balls = new ArrayList<>();
    private Timer timer;

    public BallCollision() {
        setBackground(Color.BLACK);
        timer = new Timer(DELAY, this);
        timer.start();
    }

    public static void main(String[] args) {
        JFrame frame = new JFrame("Ball Collision");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setSize(WIDTH, HEIGHT);
        frame.add(new BallCollision());
        frame.setVisible(true);
    }

    @Override
    public void actionPerformed(ActionEvent e) {
        for (Ball ball : balls) {
            ball.move();
            checkCollision(ball);
        }
        repaint();
    }

    private void checkCollision(Ball ball) {
        for (Ball otherBall : balls) {
            if (ball != otherBall && ball.intersects(otherBall)) {
                ball.reverseDirection();
                otherBall.reverseDirection();
            }
        }
    }

    @Override
    protected void paintComponent(Graphics g) {
        super.paintComponent(g);
        for (Ball ball : balls) {
            ball.draw(g);
        }
    }

    private class Ball implements Runnable {
        private int x;
        private int y;
        private int dx;
        private int dy;
        private int radius;
        private Color color;
        private Thread thread;

        public Ball(int x, int y, int dx, int dy, int radius, Color color) {
            this.x = x;
            this.y = y;
            this.dx = dx;
            this.dy = dy;
            this.radius = radius;
            this.color = color;
            thread = new Thread(this);
        }

        public void start() {
            thread.start();
        }

        public boolean intersects(Ball otherBall) {
            int distanceX = x - otherBall.getX();
            int distanceY = y - otherBall.getY();
            int radiusSum = radius + otherBall.getRadius();
            return distanceX * distanceX + distanceY * distanceY <= radiusSum * radiusSum;
        }

        public void reverseDirection() {
            dx = -dx;
            dy = -dy;
        }

        public void move() {
            if (x <= radius || x >= WIDTH - radius) {
                dx = -dx;
            }
            if (y <= radius || y >= HEIGHT - radius) {
                dy = -dy;
            }
            x += dx;
            y += dy;
        }

        public void draw(Graphics g) {
            g.setColor(color);
            g.fillOval(x - radius, y - radius, radius * 2, radius * 2);
        }

        @Override
        public void run() {
            while (true) {
                try {
                    Thread.sleep(DELAY);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
                move();
                checkCollision(this);
            }
        }

        public int getX() {
            return x;
        }

        public int getY() {
            return y;
        }

        public int getRadius() {
            return radius;
        }
    }

    public void addBall() {
        Random random = new Random();
        int x = random.nextInt(WIDTH - 50) + 25;
        int y = random.nextInt(HEIGHT - 50) + 25;
        int dx = random.nextInt(10) + 1;
        int dy = random.nextInt(10) + 1;
        int radius = random.nextInt(20) + 10;
        Color color = new Color(random.nextInt(256), random.nextInt(256), random.nextInt(256));
        Ball ball = new Ball(x, y, dx, dy, radius, color);
        balls.add(ball);
        ball.start();
    }

}

这个程序创建了一个 `BallCollision` 类，它继承了 `JPanel` 并实现了 `ActionListener` 接口。程序通过 `Timer` 定时器来触发多线程更新和绘制小球的动画效果。在 `Ball` 类中实现了小球的运动、碰撞检测和绘制方法，并通过多线程来实现小球的异步运动。程序还提供了 `addBall()` 方法用于添加新的小球。