Servlets - Problema con imagen diamica (no encuentra metodo)

Hola a todos, estoy creando un servlet que me sibuja una imagen pero tengun un error:

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type Informe de Excepción

mensaje

descripción El servidor encontró un error interno () que hizo que no pudiera rellenar este requerimiento.

excepción

javax.servlet.ServletException: La ejecución del Servlet lanzó una excepción
filters.ExampleFilter.doFilter(ExampleFilter.java:149)

causa raíz

java.lang.NoClassDefFoundError: Acme/JPM/Encoders/GifEncoder
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La cuestion es que si exixte dicho metodo y en la compilacion no da problemas, el codigo lo he ido rebajando hasta copiarme totalmente un ejemplo qeu hay en internet y que se supone que al autor si le funciona:
import javax.servlet.*;
import javax.servlet.http.*;
import java.io.*;
import java.util.*;
import java.text.*;
import java.awt.*;
import java.awt.image.BufferedImage;
import javax.swing.*;
import Acme.JPM.Encoders.*;

public class simulador extends HttpServlet {
/**Initialize global variables*/
private final static int width = 300;
private final static int height = 300;

/**Process the HTTP Get request*/
public void doGet(HttpServletRequest request, HttpServletResponse
response) throws ServletException, IOException {
response.setContentType("image/gif");
OutputStream out = response.getOutputStream();

// Create image
Image image = new BufferedImage(width, height,
BufferedImage.TYPE_INT_ARGB);

// Get Graphics context of the image
Graphics g = image.getGraphics();

drawClock(g); // Draw a clock on graphics

// Encode the image and send to the output stream
new GifEncoder(image, out, true).encode();

out.close(); // Close stream
}

private void drawClock(Graphics g) {
// Initialize clock parameters
int clockRadius =
(int)(Math.min(width, height)*0.7*0.5);
int xCenter = (width)/2;
int yCenter = (height)/2;

// Draw circle
g.setColor(Color.black);
g.drawOval(xCenter - clockRadius,yCenter - clockRadius,
2*clockRadius, 2*clockRadius);
g.drawString("12", xCenter-5, yCenter-clockRadius+12);
g.drawString("9", xCenter-clockRadius+3, yCenter+5);
g.drawString("3", xCenter+clockRadius-10, yCenter+3);
g.drawString("6", xCenter-3, yCenter+clockRadius-3);

// Get current time using GregorianCalendar
TimeZone timeZone = TimeZone.getDefault();
GregorianCalendar cal = new GregorianCalendar(timeZone);

// Draw second hand
int second = (int)cal.get(GregorianCalendar.SECOND);
int sLength = (int)(clockRadius*0.9);
int xSecond =
(int)(xCenter + sLength*Math.sin(second*(2*Math.PI/60)));
int ySecond =
(int)(yCenter - sLength*Math.cos(second*(2*Math.PI/60)));
g.setColor(Color.red);
g.drawLine(xCenter, yCenter, xSecond, ySecond);

// Draw minute hand
int minute = (int)cal.get(GregorianCalendar.MINUTE);
int mLength = (int)(clockRadius*0.75);
int xMinute =
(int)(xCenter + mLength*Math.sin(minute*(2*Math.PI/60)));
int yMinute =
(int)(yCenter - mLength*Math.cos(minute*(2*Math.PI/60)));
g.setColor(Color.blue);
g.drawLine(xCenter, yCenter, xMinute, yMinute);

// Draw hour hand
int hour = (int)cal.get(GregorianCalendar.HOUR_OF_DAY);
int hLength = (int)(clockRadius*0.6);
int xHour = (int)(xCenter +
hLength*Math.sin((hour+minute/60.0)*(2*Math.PI/12)));
int yHour = (int)(yCenter -
hLength*Math.cos((hour+minute/60.0)*(2*Math.PI/12)));
g.setColor(Color.green);
g.drawLine(xCenter, yCenter, xHour, yHour);

// Set display format in specified style, locale, and timezone
DateFormat formatter = DateFormat.getDateTimeInstance
(DateFormat.MEDIUM, DateFormat.LONG);

// Display current date
g.setColor(Color.red);
String today = formatter.format(cal.getTime());
FontMetrics fm = g.getFontMetrics();
g.drawString(today, (width -
fm.stringWidth(today))/2, yCenter+clockRadius+30);
}
}


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Alguien me puede ayudar, estoy desesperado, muchas gracias!