For loopar i Java

import java.awt.*;
import java.applet.Applet;
public class spelet extends Applet implements Runnable {
	boolean vanda = false;
	boolean tryck = false;
	int a, b, c, d;
	Button knappStop = new Button("Stopp"); // Credits to Heikki for supercoding
	Button knappRestart =new Button("Reset");
	Thread trad;
	
	
	public void init(){
		setBackground(Color.white);
		setForeground(Color.black);
		add(knappStop);
		add(knappRestart);
		}
	public boolean action(Event evt, Object arg) {
		if(evt.target instanceof Button){
			trad.stop();
		}
		return true;
	}


		
	public void start() {
		if (trad == null) {
				trad = new Thread(this);
				trad.start();
		}
	}

	public void stop() {
		if (trad != null) {
				trad.stop();
				trad = null;
		}
	}
		
	public void run(){
		for(a=0; ; a ++){
			if(vanda != true){
				for(b=20; b <180; b++){
						try{
							trad.sleep(20);
						}catch (java.lang.InterruptedException e) {
						}

						if(b >= 180){
							vanda = true;
							break;
						}
					if(tryck = true){
						trad.stop();
					}
				}
				} else {
					for(b=180; b > 20; b--){
						try{
							trad.sleep(20);
						}	catch (java.lang.InterruptedException e) {
						}	
						if(b <= 20){
							vanda = false;
							break;
						}
					}
				}
			}
		}
		
		public void paint(Graphics g){
			g.drawRect(0,0,199,199);
			if(vanda != true){
				g.setColor(Color.black);
				g.drawLine(b, 20, b, 180);
				g.setColor(Color.white);
				g.drawLine(b-1,20,b-1,180);
			} else{
				g.setColor(Color.black);
				g.drawLine(b, 20, b, 180);
				g.setColor(Color.white);
				g.drawLine(b-1,20,b-1,180);
			}
		}
}