// Introduction to Software Testing
// Authors: Paul Ammann & Jeff Offutt
// Chapter 7, page ??
// No JUnit tests at this time.

import java.io.*;
import java.util.*;

public class Stats
{

   // Example for data flow. Has some issues.
   // The calculation of mean fails with an empty numbers list.
   // The calculation of var fails with a numbers list of length one.
   public static void computeStats (int [ ] numbers)
   {
      int length = numbers.length;
      double med, var, sd, mean, sum, varsum;
   
      sum = 0.0;
      for (int i = 0; i < length; i++)
      {
         sum += numbers [ i ];
      }
      med   = numbers [ length / 2 ]; 
      mean = sum / (double) length; 
   
      varsum = 0.0;
      for (int i = 0; i < length; i++)
      {
         varsum = varsum  + ((numbers [ i ] - mean) * (numbers [ i ] - mean));
      }
      var = varsum / ( length - 1 );
      sd  = Math.sqrt ( var );
   
      System.out.println ("median:             " + med);
      System.out.println ("variance:           " + var);
      System.out.println ("standard deviation: " + sd);
   }
   
   public static void main (String []argv)
   {  // Driver method for computeStats
      int [] numbers1 = new int[] {1, 5, 7, 9, 10, 15};
      System.out.println ("TEST 1");
      System.out.println ("Input: " + Arrays.toString(numbers1));
      computeStats (numbers1);
   
      System.out.println ("\n----------------------------------");
      int [] numbers2 = new int[] {42};
      System.out.println ("TEST 2");
      System.out.println ("Input: " + Arrays.toString(numbers2));
      computeStats (numbers2);
   
      System.out.println ("\n----------------------------------");
      int [] numbers3 = new int[] {};
      System.out.println ("TEST 3");
      System.out.println ("Input: " + Arrays.toString(numbers3));
      try
      { // Expect ArrayIndexOutOfBoundsException
         computeStats (numbers3); // Throws ArrayIndexOutOfBoundsException
      }
      catch (ArrayIndexOutOfBoundsException e)
      {
         System.out.println ("ArrayIndexOutOfBoundsException thrown.");
      }
   
      // This doesn't compile
      // System.out.println ("\n----------------------------------");
      // int [] numbers4;
      // System.out.println ("TEST 4");
      // System.out.println ("Input: " + Arrays.toString(numbers4));
      // computeStats (numbers4);
   }
}