How to Efficiently Animate Multiple Bouncing Balls in Java Without Overlapping?

Java Bouncing Ball

Problem:

When drawing multiple balls on the screen that bounce off the edges of the frame, the second ball overwrites the initial ball.

Given Code:

The provided code attempts to draw multiple bouncing balls, but the second ball overwrites the initial ball.

With the current approach, the following issues are present:

• Opaque components are placed on top of each other.
• A layout manager isn't specified, which affects the placement of the balls.
• The control of the ball's size and location is not handled effectively.
• Speed and location of the balls aren't randomized.
• Updates of the ball should be performed within the context of the EDT.
• X/Y values aren't necessary, as the panels can be used.

Scalability Issues with Multiple Threads:

The current approach involves creating a separate thread for each ball. This can strain system resources, especially when the number of balls increases.

Alternative Approach:

Instead of using components for each ball, consider creating a container for the balls and using a simple animation loop to update their positions and redraw them. This approach is more scalable.

Implementation:

Here's an alternative implementation that addresses the issues mentioned above:

public class AnimatedBalls {

    public static void main(String[] args) {
        new AnimatedBalls();
    }

    public AnimatedBalls() {
        EventQueue.invokeLater(() -> {
            JFrame frame = new JFrame("Bouncing Balls");
            frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
            frame.setSize(400, 400);
            frame.setVisible(true);

            // Create a container for the balls
            BallsPane ballsPane = new BallsPane();
            frame.add(ballsPane);
        });
    }

    public class BallsPane extends JPanel {

        private List<Ball> balls;

        public BallsPane() {
            balls = new ArrayList<>();

            for (int i = 0; i < 10; i++) {
                Random random = new Random();
                int x = (int) (Math.random() * getWidth());
                int y = (int) (Math.random() * getHeight());
                int vx = (int) (Math.random() * 10) - 5;
                int vy = (int) (Math.random() * 10) - 5;
                Ball ball = new Ball(x, y, vx, vy);
                balls.add(ball);
            }
        }

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

            for (Ball ball : balls) {
                ball.draw(g);
            }
        }

    }

    public class Ball {

        private int x;
        private int y;
        private int vx;
        private int vy;

        public Ball() {
            this(0, 0, 0, 0);
        }

        public Ball(int x, int y, int vx, int vy) {
            this.x = x;
            this.y = y;
            this.vx = vx;
            this.vy = vy;
        }

        public void update() {
            // Bounce off the edges of the frame
            if (x < 0 || x > getWidth())
                vx *= -1;
            if (y < 0 || y > getHeight())
                vy *= -1;

            // Update the ball's position
            x += vx;
            y += vy;
        }

        public void draw(Graphics g) {
            // Draw the ball as a filled circle
            g.setColor(Color.RED);
            g.fillOval(x - 5, y - 5, 10, 10);
        }

    }

}

In this alternative implementation:

• A single animation loop updates all the balls.
• The balls are represented by simple data structures (not components).
• The animation loop handles bounding off the edges of the frame.
• Randomization is used to vary the starting speed and location of the balls.
• The update() method calculates the new position of each ball.
• The draw() method renders the ball as a filled circle.

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