//MY
import java.awt.*;

public class pp {
	public static void main(String args[]) {
		Frame w = new Frame();
		w.setSize(300, 400);
		MyPanel mp = new MyPanel();
		w.add(mp);

		Thread t = new Thread(mp);
		t.start();

		w.show();
	}
}

class MyPanel extends Panel implements Runnable {
	int x = 30;
	int y = 30;
	int att = 0;

	public void paint(Graphics g) {
	 
	 g.fillOval(x, y, 20, 30); }
	

	public void run() {
		while (true) {
			//定义状态
			if(att==0)
			{
				x++;
				y++;
			}
			if(att==1)
			{
				x--;
				y++;
			}
			if(att==2)
			{
				x--;
				y--;
			}
			if(att==3)
			{
				x++;
				y--;
			}
			//改变状态
			if (x > 263) {
				if (att == 0) 
					att = 1;
				else 
					att = 2;
			}
				if (y > 348) {
					if (att == 1) 
						att = 2;
					 else 
						att = 3;
				}
					if (x < 0) {
						if (att == 2) 
							att = 3;
						else 
							att = 0;
					}
					
					if (y < 0) {
						if (att == 3) 
							att = 0;
						else 
							att = 1;
				}

			
			try {
				Thread.sleep(10);
			} catch (Exception e) {
			}
			
			repaint();
		}
		}
	}