/*
 * Write an application that creates an int array of 
 * size 1000000, assigns a random integer between + and 
 * -10000 to each and computes the mean and 
 * standard deviation as decimal values.
 * Print those to the user.
 * 
 * Mean: 
 * (sum of all values) / (number of values)
 * 
 * Standard Deviation: 
 * The square root of 
 *    the average of 
 *      the squared differences of 
 *         each value from the mean.
 * 
 */

public class StandardDeviation{
  public static void main(String[] args){
    
    int[] values = new int[1000000];
    final int MIN_VALUE = -10000;
    final int MAX_VALUE = 10000;
    double valuesSum = 0.0, sqDiffSum = 0.0, mean, standardDev;
    
    // Set each element in values equal to a random
    // integer between MIN_VALUE and MAX_VALUE
    
    
    // Compute the sum of all elements in values,
    // such the sum gets stored in valuesSum
    
    
    
    // Compute the mean (average) of all values
    // and store in the variable mean

    
    // Compute the sum of the squared differences
    // of each value from the mean.  Conceptually,
    // this looks like:
    //    (first - mean)^2 + 
    //    (second - mean)^2 + 
    //    (third - mean)^2 + 
    //    ....... +
    //    (last - mean)^2 + 
    
    
    
    
    // Compute the standard deviation, which is the 
    // square root of the result of dividing the sum of 
    // squared differences by the total number of values

    
    
    System.out.println("Mean:               " + mean);
    System.out.println("Standard Deviation: " + standardDev);
    
  }
  
  private static int randomIntInRange(int low, int high) {
    
    int multiplier = high - (low - 1);
    return (int)(Math.random() * multiplier) + low;
    
  }
  
}

Program output example:

> run StandardDeviation
Mean:               -3.77569
Standard Deviation: 5779.955079273639