import java.awt.*;

public class Piston extends java.applet.Applet{ 
   Image pvtpics[] = new Image[14];
   Image currentimg;
   Thread runner;
   int xpos = 125;
   int ypos=50;
   int i=0;
 
   public void init() {
       String pvtsrc[] = {"pistm1.gif", "pistm2.gif", "pistm3.gif", 
       "pistm4.gif", "pistm5.gif", "pistm6.gif",
       "pistm7.gif", "pistm8.gif", "pistm9.gif", "pistm10.gif",
       "pistm11.gif", "pistm12.gif", "pistm13.gif", "pistm14.gif"};

       for (int i=0; i<pvtpics.length;i++) {
          pvtpics[i]=getImage(getCodeBase(),pvtsrc[i]);
       }
        add(new Button("add heat"));
        add(new Button("remove heat"));
}
       public void start() {
       setBackground(Color.white);
       i=0;
       currentimg=pvtpics[i];
       repaint();
       }
       public boolean action(Event evt, Object arg){
            if(evt.target instanceof Button){
            doButton((String)arg);
            return true;
           } else return false;
        }

        void doButton(String bname){
        if(bname.equals("add heat")) {
        i=i+1;
        if(i>13) i=13;
        currentimg=pvtpics[i];}
        if(bname.equals("remove heat")){
        i=i-1;
        if(i<0) i=0;
        currentimg=pvtpics[i];}
        repaint();
        }
    
    public void paint(Graphics g) {
      if (currentimg != null)
      g.drawImage(currentimg, xpos, ypos, this);
    }
}