import java.awt.*;

public class Graph2 extends java.applet.Applet implements Runnable
{
	int step = 0;
	Thread mainThread;
	// An offscreen image
	Image offscreen;
	boolean pause = false;
	public void init()
	{
		// Create the offscreen image
		offscreen = createImage(360, 180);
		// Clear it
		Graphics g = offscreen.getGraphics();
		clearImage(g);
		// Now create a thread for the action to happen in
		mainThread = new Thread(this);
		mainThread.start();
		
	}
	public void update(Graphics g)
	{
		paint(g);		
	}
	synchronized public void paint(Graphics g)
	{
		// Just copy the offscreen image to the screen.
		g.drawImage(offscreen, 0, 0, this);
	}		
	synchronized void drawCurrentStep() {
		// Get a "pen" for our offscreen image
		Graphics g = offscreen.getGraphics();
		// Clear the image
		clearImage(g);
		// Set the drawing color for the curve
		g.setColor(Color.red);
		int x;
		// Use this to remember the last position so we 
		// can draw a line back to it. We have to give it
		// an initial value or the compiler will complain.
		int oldy = 0;
		// Trig refresher course!
		for (x = 0; (x < 360); x += 4) {
			double degrees = x + step;
			// Convert degrees to radians
			double radians = degrees * .0174532925;
			int y = (int) (Math.sin(radians) * 90) + 90;
			// Draw a red line from this value to the previous one,
			// if any
			if (x > 0) {
				g.drawLine(x - 4, oldy, x, y);
			}
			// Remember this position for the next line
			oldy = y;
		}
	}	
	public void run()
	{
		while (true) {
			if (pause) {
				// Sleep a lot when paused
				try {
					mainThread.sleep(100);	
				} catch (Exception e) {
					// Nothing will be interrupting us,
					// so just catch and do nothing here
				}
			} else {	
				// Move and draw
				moveOneStep();
				drawCurrentStep();
				repaint();
			}
		}
	}
	void moveOneStep()
	{
		step++;
		if (step == 360) {
			step = 0;
		}
		try {
			mainThread.sleep(50);	
		} catch (Exception e) {
			// Nothing will be interrupting us,
			// so just catch and do nothing here
		}
	}
	void clearImage(Graphics g)
	{
		// Clear the image
		g.setColor(Color.black);
		g.fillRect(0, 0, 360, 180);
	}
	public void start()
	{
		// This is called by the browser
		// when the user returns to this
		// web page, and also once right
		// after init(). Clear the
		// pause flag.
		pause = false;
	}
	public void stop()
	{
		// This is called by the browser
		// when the user leaves this
		// web page. Set the pause flag
		// to avoid wasting CPU.
		pause = true;
	}
	public void destroy()
	{
		// This is called by the browser
		// when the web page is being
		// thrown out of cache and the
		// applet is discarded. It is our
		// task to stop our thread.
		mainThread.stop();
	}
};