when i run my program this message appears "Exception in thread "main" java.lang.NoClassDeFoundError: org/javadevices/javaclass/ArrayTest5



//The purpose of this program is to demonstrate the use of some simple arrays.

//This package command is more like what one would expect to find when dealing with
// Java applications or libraries that are meant to be widely used.
package org.javadevices.javaclass;


public class ArrayTest5
{

  public ArrayTest5()
  {
    super();
  }//end constructor


  //This method accepts a String array which contains tool names and and an
  // integer array which contains the weight in grams for these tools. Each
  // tool name is then printed to standard out along with its weight and the
  // number of characters in its name.
  public void printTools(String[] pTools, int[] tWeights)
  {
    int[] toolsLetterCount = getLetterCount(pTools);

    int arrayLength = pTools.length;

    for (int x = 0; x < arrayLength; x++)
    {
      System.out.println(pTools[x] + " - " + tWeights[x] + " grams - " + toolsLetterCount[x] + " letters");
    }// end for

  }//end method


  //This method accepts a String array and it returns a new integer array
  // which contains the letter count for each word in the String array.
  public int[] getLetterCount(String[] words)
  {

    //Create a new empty integer array which has the same number of members
    // as the String array that was passed into this method.
    int[] letterCount = new int[words.length];

    int x = 0;
    while (x < words.length)
    {
      letterCount[x] = words[x].length();
      x++;
    }//end while

    return letterCount;
  }//end method



  public static void main(String[] args)
  {
    ArrayTest5 at = new ArrayTest5();

    //Create a reference of type "String array" called 'tools' and then also
    // create a new String array object and have 'tools' refer to it. Notice that
    // an array can be initialized when it is created by placing the array
    // members in braces.
    String[] tools = new String[] {"hammer", "wrench", "screwdriver", "hacksaw", "pliers"};

    //Create a reference of type "int array" called 'toolWeights' and then
    // also create a new int array object and have 'toolWeights' refer to it.
    // Notice that an array can be initialized when it is created by
    // placing the array members in braces.
    int[] toolWeights = new int[] {510,102,105,331,233};

    at.printTools(tools, toolWeights);

  }//end main

}//end class