import java.applet.*;
import java.awt.*;

/* Moving Radar Beam with Double Buffering 

	(this will remove any flicker)
*/


public class RadarBeamDB extends Applet implements Runnable
{
// notice the "implements runnable", this is needed for using threads



	Thread t;	
	// create a field that will be used for an instance of a thread

	private int startAngle;

	private Image bufferImage;
	private Graphics buffer;
	// create a graphics buffer and off screen image

	private int width;
	private int height;

	public void init()
	{
		setBackground(Color.black);

		t=new Thread(this);
		// instantiate a new thread object

		t.start();
		// start our thread running

		startAngle=90;
		// start at the top of the screen

		width=size().width;
		height=size().height;
	
		bufferImage=createImage(width, height);
		buffer = bufferImage.getGraphics();
		// create off screen buffer image and place it in the buffer

	}

	public void run()
	{
		while(true)
		{
			repaint(); 

			try{
				t.sleep(5);
			}catch(InterruptedException e){ ; }		
			
			startAngle++;			
		}
	}

	public void paint(Graphics g)
	{

		if (buffer == null) 
		{
		// make sure the buffer was setup correctly
			bufferImage = createImage(width, height);
			buffer = bufferImage.getGraphics();
		}


		buffer.setColor(Color.black);
		buffer.fillRect(0,0, width, height);
		// draw our background square to the buffer

		buffer.setColor(Color.red);
		buffer.fillArc(0,0, size().width, size().height, startAngle, 30);
		// fillArc(int x, int y, int width, int height, int startAngle, int arcAngle)	


		g.drawImage(bufferImage, 0, 0, this);
		// draw our buffer image to the applet
	}

	public void update(Graphics g)
	{
	// the update method will be called automatically to redraw the applet
		paint(g);

	}
}