ArraysAndRandomNumbers.java

package org.drip.zen.juice;

/*
 * 1) Concept of Random Number
 * 2) Generate a Random Number between 0 and 1
 * 3) Concept of evenly distributed Random Number between Left and Right
 * 4) Generate a Random Number between "Lower Bound" and "Upper Bound"
 * 5) Concept of an Array - syntax and Usage
 * 6) Generate an Array of bounded Random Numbers
 * 7) Concept of Distribution of Buckets
 */

public class ArraysAndRandomNumbers {

    static double RandomNumber0_1()
    {
        return Math.random();
    }

    static double RandomNumber (double lowerBound, double upperBound)
    {
        double randomNumber = lowerBound + (upperBound - lowerBound) * RandomNumber0_1();

        return randomNumber;
    }

    static double[] RandomNumberArray (double lowerBound, double upperBound, int arraySize)
    {
        double[] randomArray = new double[arraySize];

        for (int counter = 0; counter < arraySize; counter = counter + 1)
        {
            randomArray[counter] = RandomNumber (lowerBound, upperBound);
        }

        return randomArray;
    }

    static int[] QuartileDistribution (double lowerBound, double upperBound, double[] randomNumberArray)
    {
        int numberOfBuckets = 4;
        int[] quartileBuckets = new int[numberOfBuckets];
        int arraySize = randomNumberArray.length;
        double bucketWidth = (upperBound - lowerBound) / numberOfBuckets;

        for (int counter = 0; counter < arraySize; counter = counter + 1)
        {
            double randomNumber = randomNumberArray[counter];

            if (randomNumber >= lowerBound && randomNumber < lowerBound + bucketWidth)
                quartileBuckets[0] = quartileBuckets[0] + 1;
            else if (randomNumber >= lowerBound + bucketWidth && randomNumber < lowerBound + 2 * bucketWidth)
                quartileBuckets[1] = quartileBuckets[1] + 1;
            else if (randomNumber >= lowerBound + 2 * bucketWidth && randomNumber < lowerBound + 3 * bucketWidth)
                quartileBuckets[2] = quartileBuckets[2] + 1;
            else if (randomNumber >= lowerBound + 3 * bucketWidth && randomNumber <= upperBound)
                quartileBuckets[3] = quartileBuckets[3] + 1;
        }

        return quartileBuckets;
    }

    public static void main (String[] input)
    {
        double myLowerBound = 0;
        double myUpperBound = 100;
        int myArraySize = 100000;

        double[] myRandomNumberArray = RandomNumberArray (myLowerBound, myUpperBound, myArraySize);

        int[] myQuartileBuckets = QuartileDistribution (myLowerBound, myUpperBound, myRandomNumberArray);

        System.out.println ("\tFirst Quartile  : " + myQuartileBuckets[0] + " | " + (100. * myQuartileBuckets[0] / myArraySize) + "%");

        System.out.println ("\tSecond Quartile : " + myQuartileBuckets[1] + " | " + (100. * myQuartileBuckets[1] / myArraySize) + "%");

        System.out.println ("\tThird Quartile  : " + myQuartileBuckets[2] + " | " + (100. * myQuartileBuckets[2] / myArraySize) + "%");

        System.out.println ("\tFourth Quartile : " + myQuartileBuckets[3] + " | " + (100. * myQuartileBuckets[3] / myArraySize) + "%");
    }
}