bandwith detection in java program

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Java

import java.util.Vector;
import java.util.Date;
import java.util.Enumeration;
import java.applet.Applet;

class DataSample {
  long byteCount;
  Date start;
  Date end;

  DataSample(long bc, Date ts, Date tf) {
    byteCount = bc;
    start = ts;
    end = tf;
  }
}

public class DataMonitor {
  protected Vector samples;
  protected Date epoch;

  public DataMonitor() {
    samples = new Vector();
    epoch = new Date();
  }

  // Add a sample with a start and finish time.
  public void addSample(long bcount, Date ts, Date tf) {
    samples.addElement(new DataSample(bcount, ts, tf));
  }

  // Get the data rate of a given sample.
  public float getRateFor(int sidx) {
    float rate = 0.0;
    int scnt = samples.size();
    if (scnt > sidx && sidx >= 0) {
      DataSample s = samples.elementAt(sidx);
      Date start = s.start;
      Date end = s.end;
      if (start == null && sidx >= 1) {
        DataSample prev = samples.elementAt(sidx - 1);
        start = prev.end;
      }

      if (start != null && end != null) {
        long msec = end.getTime() - start.getTime();
        rate = 1000 * (float)s.byteCount / (float)msec;
      }
    }

    return rate;
  }

  // Get the rate of the last sample
  public float getLastRate() {
    int scnt = samples.size();
    return getRateFor(scnt - 1);
  }

  // Get the average rate over all samples.
  public float getAverageRate() {
    long msCount = 0;
    long byteCount = 0;
    Date start;
    Date finish;
    int scnt = samples.size();
    for (int i = 0; i < scnt; i++) {
      DataSample ds = (DataSample)samples.elementAt(i);

      if (ds.start != null)
        start = ds.start;
      else if (i > 0) {
        DataSample prev = (DataSample)samples.elementAt(i-1);
        start = ds.end;
      }
      else
        start = epoch;

      if (ds.end != null)
        finish = ds.end;
      else if (i < scnt - 1) {
        DataSample next = (DataSample)samples.elementAt(i+1);
        finish = ds.start;
      }
      else
        finish = new Date();

      // Only include this sample if we could figure out a start
      // and finish time for it.
      if (start != null && finish != null) {
        byteCount += ds.byteCount;
        msCount += finish.getTime() - start.getTime();
      }
    }

    float rate = -1;
    if (msCount > 0) {
      rate = 1000 * (float)byteCount / (float)msCount;
    }

    return rate;
  }
}

Q: when i run this code it was showing applet is not initiated!.....why this error...plz help..
my package name is Bandwidth and my class/file name is DataSample.java
these r the errors*:

run:
load: class Bandwidth/DataSample.class not found.
java.lang.ClassNotFoundException: Bandwidth.DataSample.class
	at sun.applet.AppletClassLoader.findClass(AppletClassLoader.java:183)
	at java.lang.ClassLoader.loadClass(ClassLoader.java:306)
	at sun.applet.AppletClassLoader.loadClass(AppletClassLoader.java:127)
	at java.lang.ClassLoader.loadClass(ClassLoader.java:251)
	at sun.applet.AppletClassLoader.loadCode(AppletClassLoader.java:626)
	at sun.applet.AppletPanel.createApplet(AppletPanel.java:780)
	at sun.applet.AppletPanel.runLoader(AppletPanel.java:709)
	at sun.applet.AppletPanel.run(AppletPanel.java:363)
	at java.lang.Thread.run(Thread.java:619)
Caused by: java.io.FileNotFoundException: C:\Users\DEBASISH\Documents\NetBeansProjects\DataMonitor\build\classes\Bandwidth\DataSample\class.class (The system cannot find the path specified)
	at java.io.FileInputStream.open(Native Method)
	at java.io.FileInputStream.<init>(FileInputStream.java:106)
	at java.io.FileInputStream.<init>(FileInputStream.java:66)
	at sun.net.www.protocol.file.FileURLConnection.connect(FileURLConnection.java:70)
	at sun.net.www.protocol.file.FileURLConnection.getInputStream(FileURLConnection.java:161)
	at sun.applet.AppletClassLoader.getBytes(AppletClassLoader.java:295)
	at sun.applet.AppletClassLoader.access$100(AppletClassLoader.java:44)
	at sun.applet.AppletClassLoader$1.run(AppletClassLoader.java:173)
	at java.security.AccessController.doPrivileged(Native Method)
	at sun.applet.AppletClassLoader.findClass(AppletClassLoader.java:170)
	... 8 more
BUILD SUCCESSFUL (total time: 11 seconds)