Say that you have a file containing 100 integers, one integer per line. You wish to add up all these integers. You can write a program to add numbers from keyboard input. Once it has been tested and debugged, it can be used with the input file. Here is a start on the program:

import java.util.Scanner;

class AddUpFile
{
  public static void main ( String[] args )  
  {
    Scanner scan = new Scanner( System.in );
    int value;
    int sum = ; // initialize sum

    int count = ; // initialize count
    while ( count  100 )
    {
      System.out.print("Enter a number: ");
      value  = scan.nextInt();
      sum    = ; // add to the sum
      count  = ; // increment count
    }

    System.out.println( "Grand Total: " + sum );
  }
}