java swing模仿随机频谱

import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.image.BufferedImage;
import java.util.Random;

import javax.swing.JFrame;
import javax.swing.JPanel;

public class Main extends JFrame {
	public static void main(String[] args) {
		new Main();
	}
	WavePanel panel = new WavePanel();
	public Main() {
		setDefaultCloseOperation(EXIT_ON_CLOSE);
		setLayout(new BorderLayout());
		add(panel);
		pack();
		setLocationRelativeTo(null);
		setVisible(true);
		new Thread(new Runnable() {
			public void run() {
				try {
					while (true) {
						Thread.sleep(100);
						panel.repaint();
					}
				} catch (InterruptedException e) {
					e.printStackTrace();
				}
			}
		}).start();
	}
	class WavePanel extends JPanel {
		final int bufWidth = 400, bufHeight = 200;
		final int len = 100;
		final int lifeLine = (int) (bufWidth * 0.75);
		final int midHeight = bufHeight >> 1;
		final int perw = lifeLine / len;
		final BufferedImage buf = new BufferedImage(bufWidth, bufHeight,
				BufferedImage.TYPE_INT_ARGB);
		final int a[] = new int[len];
		final Random random = new Random();
		public int ai = 0;
		public WavePanel() {
			setPreferredSize(new Dimension(bufWidth, bufHeight));
		}
		@Override
		protected void paintComponent(Graphics g) {
			ai = (ai + 1) % len;
			a[ai] = random.nextInt(100);
			Graphics gg = buf.getGraphics();
			gg.clearRect(0, 0, buf.getWidth(), buf.getHeight());
			gg.setColor(Color.RED);
			for (int i = 0; i < len; i++) {
				int j = (ai - i + len) % len;
				int leftSpace = perw / 3;
				int x = lifeLine - i * perw;
				int y = midHeight - (a[j] >> 1);
				int w = (int) (0.6 * perw), h = a[j];
				gg.fillRect(x - leftSpace, y, w, h);
			}
			gg.setColor(Color.CYAN);
			gg.drawLine(lifeLine, 0, lifeLine, bufHeight - 1);
			g.drawImage(buf, 0, 0, null);
		}
	}
}