import java.awt.Frame;
import java.awt.Color;
import java.awt.Graphics;
import java.awt.Image; // Used to create an image buffer
import java.awt.event.WindowAdapter;
import java.awt.event.WindowEvent;
import java.awt.Graphics2D; // Used for anti-aliasing
import java.awt.RenderingHints; // Used for anti-aliasing

public class GraphicsMoveObjectsWithThreadAndFrame extends Frame implements Runnable
{
	Image image;
	Graphics graphics;
	int width = 400, height = 250;
	int dotSize = 25, dotBlueX = 150, dotBlueY = 70, dotMagentaX = 230, dotMagentaY = 190;
	int directionBlue = 1, speedBlue = 2, directionMagenta = 1, speedMagenta = 4;

	public static void main(String[] args)
	{
		// Create a thread containing an instance of the
		//  'GraphicsMoveObjectsWithThreadAndFrame' class
		//  and set the frame background color
		GraphicsMoveObjectsWithThreadAndFrame frame = new GraphicsMoveObjectsWithThreadAndFrame();
		frame.setBackground(Color.WHITE);
		new Thread(frame).start();
	}

	// Constructor
	public GraphicsMoveObjectsWithThreadAndFrame()
	{
		this.setSize(width, height);
		this.setTitle("Object Movement with a Thread on a Frame");
		this.setLocationRelativeTo(null);
		this.setResizable(false);
		this.setVisible(true);

		// Close and destroy the window (frame) when a closing event is
		//  detected; without this section of code, it can be difficult
		//  for a user to end the program and make the frame go away;
		//  note that with a JFrame (as opposed to a Frame), closing a
		//  window can be handled with a single line of code
		addWindowListener(new WindowAdapter()
		{
			public void windowClosing(WindowEvent e)
			{
				e.getWindow().dispose();
				System.exit(0);
			}
		});
	}

	// Since a timer is not being used, this method should be set to
	//  continuously repeat (loop); a thread is used (below) to pause
	//  the loop, which effectively simulates a timer with an interval 
	public void run()
	{
		while (true)
		{
			// Update the position/direction of the blue dot 
			dotBlueX += speedBlue * directionBlue;
			if (dotBlueX < 16 || dotBlueX > width - 18)
				directionBlue = -directionBlue;

			// Update the position/direction of the magenta dot
			dotMagentaX += speedMagenta * directionMagenta;
			if (dotMagentaX < 16 || dotMagentaX > width - 18)
				directionMagenta = -directionMagenta;

			repaint();

			try
			{
				// Pause for 15/1000 seconds (so that the dots do not move
				//  across the frame too quickly
				Thread.sleep(15);
			}
			catch (InterruptedException e)
			{
				// This section is required when using 'Thread.sleep()'
			}
		}
	}

	public void paint(Graphics g)
	{
		// Prepare to create the image on a separate 'Image' instance; this
		//  should prevent flickering by using a "buffer" on which the frame
		//  image will first be drawn before it is displayed to the user
		image = createImage(width, height);
		graphics = image.getGraphics();

		// This line causes graphics and text to be rendered with anti-aliasing
		//  turned on, making the overall display look smoother and cleaner
		((Graphics2D) graphics).setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);

		// Draw/Redraw the blue dot
		graphics.setColor(Color.BLUE);
		graphics.fillOval(dotBlueX - dotSize / 2, dotBlueY - dotSize / 2, dotSize, dotSize);

		// Draw/Redraw the magenta dot
		graphics.setColor(Color.MAGENTA);
		graphics.fillOval(dotMagentaX - dotSize / 2, dotMagentaY - dotSize / 2, dotSize, dotSize);

		// Display (Draw) the buffered image on the frame
		g.drawImage(image, 0, 0, null);
	}
}