Breaking the Program

Debugging a program is often difficult. Finding test cases that thouroughly test a program is an important part of this.

Here is our program, again:

class MaxAlgorithm
{
  public static void main ( String[] args ) 
  {
    int[] array =  { -20, 19, 1, 5, -1, 27, 19, 5 } ;
    int   max;

    // initialize the current maximum
    max = array[0];

    // scan the array
    for ( int index=0; index < array.length; index++ )
    { 
      if ( array[ index ] > max )    // examine the current element
        max = array[ index ];        // if it is the largest so far, change max
    }     
    System.out.println("The maximum of this array is: " + max );
  }
}      

Compile and run the program. Once you have it running see if you can "break" it by initializing the array to different values:

• Put the largest element at the beginning.
• Put the largest element at the end.
• Put in more than one copy of the largest element.
• Put in an extremely large element.
• Make all elements the same.
• Make all elements negative.
• Make all elements zero.

Is the correct maximum found in each case? Sometimes a program works for the data a programmer was thinking about when the program was written, but not for all the kinds of data the program is used with.