NoClassDefFoundError

I am new to Java programming, and I seem to still be struggling with the OOP nature of it.  I figure that has something to do with the error that I am currently getting.

Basically, this program creates an applet that displays a checker board with 24 pieces on it.  Eventually, more will be able to be done with the individual pieces (thus, my reasoning for storing all of the data on each in an array).

When I try running this program, I am getting a NoClassDefFound Error.  Any thoughts on what I can do to fix the problem?

Also, I know that as the code is now, the Checkers will not show up.  That's the next step after this.  Thanks.


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

class Checker{
    String color;
    int crowned;
    int xloc;
    int yloc;
  public Checker(){
    color=null;
    crowned=0;
    xloc=0;
    yloc=0;
  }
}

public class Proj5 extends Applet implements Runnable{
  Thread kicker;
  int x0,y0,x,y;
  int color=1;
  Checker[] pieces = new Checker[24];
  public void paint(Graphics g){
    for(int i=0;i<8;i++){
      for(int j=0;j<8;j++){
        color=color*-1;
        if(color==1){
          g.setColor(Color.blue);
         }
        if(color==-1){
          g.setColor(Color.orange);
        }
        g.fillRect(x,y,40,40);
        x=x+40;
      }
      color=color*-1;
      x=x0;
      y=y+40;
    }
  }

  public void init(){
    x0=20;
    y0=20;
    x=x0;
    y=y0;
    int blah=1;
    int num=0;
    for(int i=0;i<8;i++){
      for(int j=0;j<8;j++){
        blah=blah*-1;
          if((blah==1)&&(i<3)){
            pieces[num].xloc=x+10;
            pieces[num].yloc=y+10;
            pieces[num].color="red";
          }
          if((blah==1)&&(i>4)){
            pieces[num].xloc=x+10;
            pieces[num].yloc=y+10;
            pieces[num].color="black";
          }
        }
        x=x+40;
        num++;
      }
    blah=blah*-1;
    x=x0;
    y=y+40;
  }

   /*
    addMouseListener(new MouseAdapter(){
      public void mouseClicked(MouseEvent e){

  }*/

  public void run(){
    while(kicker!=null){
      repaint();
    }
  }
}