RandomizeNumberArray.java

import java.util.*;

public class RandomizeNumberArray {

    /**
    *       Program:        RandomizeNumberArray.java
    *       Purpose:        Randomize an array of integers
    *       Creator:        Chris Clarke
    *       Created:        25.10.2012
    */

    public static void main(String[] args) {
        Scanner scan = new Scanner(System.in);
        int min = 0; // makes the range from 0 to max-1
        int max = 0;

        System.out.print("Enter size of the array: ");

        try {
            max = scan.nextInt();

        } catch (Exception x) {
            System.out.println("Not a whole number!");
            System.exit(1);
        } // end try/catch

        // randomize the order of an array of linear values
        int[] shuffled = randomizeOrder(min, max);

        System.out.println(); // new line

        // display contents of array
        for (int i=0; i<max; i++) {
            System.out.print(shuffled[i]+" ");
        } // end for

        System.out.println(); // new line
    } // end main

    public static int[] randomizeOrder(int min, int max) {

        /**
        *   max is the array size
        *   when min=0, range is 0 to max-1
        *   shuffle or rearrange the array values
        */

        int[] theArray, results;
        theArray = new int[max];
        results = new int[max];

        int r;  // a random number

        // initialise the array
        for (int i=0; i<max; i++)
            theArray[i]=i+min; // when min=1, range is 1 to max inclusive
                       // when min=0, range is 0 to max-1 inclusive

        // pick n numbers
        for (int i=0; i<max; i++) {
            // range 1 to 49, 1 to 48 etc
            r = (int) ((max-i) * Math.random());
            // store results
            results[i] = theArray[r];
            // move last number in theArray to position r
            theArray[r] = theArray[max-1-i];
        } // end for

        return results;

    } // end randomizeOrder
} // end class