53 lines
1.5 KiB
Java
53 lines
1.5 KiB
Java
import java.awt.*;
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import javax.swing.*;
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public class Pendulum extends JPanel implements Runnable {
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private double angle = Math.PI / 2;
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private int length;
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public Pendulum(int length) {
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this.length = length;
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setDoubleBuffered(true);
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}
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@Override
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public void paint(Graphics g) {
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g.setColor(Color.WHITE);
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g.fillRect(0, 0, getWidth(), getHeight());
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g.setColor(Color.BLACK);
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int anchorX = getWidth() / 2, anchorY = getHeight() / 4;
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int ballX = anchorX + (int) (Math.sin(angle) * length);
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int ballY = anchorY + (int) (Math.cos(angle) * length);
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g.drawLine(anchorX, anchorY, ballX, ballY);
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g.fillOval(anchorX - 3, anchorY - 4, 7, 7);
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g.fillOval(ballX - 7, ballY - 7, 14, 14);
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}
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public void run() {
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double angleAccel, angleVelocity = 0, dt = 0.1;
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while (true) {
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angleAccel = -9.81 / length * Math.sin(angle);
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angleVelocity += angleAccel * dt;
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angle += angleVelocity * dt;
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repaint();
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try { Thread.sleep(15); } catch (InterruptedException ex) {}
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}
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}
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@Override
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public Dimension getPreferredSize() {
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return new Dimension(2 * length + 50, length / 2 * 3);
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}
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public static void main(String[] args) {
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JFrame f = new JFrame("Pendulum");
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Pendulum p = new Pendulum(200);
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f.add(p);
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f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
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f.pack();
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f.setVisible(true);
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new Thread(p).start();
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}
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}
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