/** An Example of some array manipulation 
 **/

public class ArrayExample {

  public static void main (String args[]) {

    int numberOfElements = 0;
    if (args.length > 0) {
      // Use value from command line
      numberOfElements = Integer.parseInt(args[0]);
    }

    ArrayExample anExample = new ArrayExample();

    anExample.initializeArray(numberOfElements);

    // Notice that method calls can be included in other method
    // calls: in this case, returning primitive values that will
    // be converted to String objects.

    System.out.println("sum = " + anExample.Sum() + 
                       " average = " + anExample.Average() );
  }

  private int[] intArray; // all instance (non static) methods
                          // have acess to this 'instance' variable

  /** Initialize the array (which will be made big enough to hold
      size entries) contents with some numbers */
  public void initializeArray(int size) {

    intArray = new int[size];

    int startValue = size * 3;          // pick any number

    for (int i = 0; i < intArray.length; i++) {
      intArray[i] = startValue; // put current number in next slot
      startValue = startValue - 2; // and calculate next number
    }
  }

  /** Calculate the sum of the array contents */
  public long Sum() {
    int index;
    int arrayLen;
    long sum = 0;

    // All arrays have a length field that specifies how many
    // elements the array contains

    arrayLen = intArray.length;

    // Calculate the sum the values in all array elements

    for (index = 0; index < arrayLen; index++) {
      sum += intArray[index];
    }
    return sum;
  }

  /** Calculate the average of the array contents */
  public double Average() {

    // Notice that Average calls Sum() to total the values in the
    // array, rather than duplicating that calculation here.  What
    // is going on with the "(double)" ?

    double average = (double) Sum() / intArray.length;
    return average;
  }

}