BE THE CODER > Java > Random Numbers and Shuffling

The following code shows the generation of random numbers with in some range and suffling the user provided list. The logic is that we randomly pick a number from the given range and add to the final list. This process continues util all elements in the range are processed.

File Name :	com/bethecoder/tutorials/random/Shuffle.java
Author :	Sudhakar KV
Email :	[email protected]


package com.bethecoder.tutorials.random;



import java.util.ArrayList;

import java.util.Arrays;

import java.util.List;



public class Shuffle {



  public static void main(String[] args) {

      

    List<Integer> shuffledItems = shuffle(1, 10);

    System.out.println(shuffledItems);

    

    List<String> shuffledStringItems = shuffle(Arrays.asList(new String [] {

        "one", "two", "three", "four", "five", "six", "seven", "eight"    

    }));

    

    System.out.println(shuffledStringItems);

  }

  

  public static List<Integer> shuffle(Integer start, Integer count) {

    

    List<Integer> items =  new ArrayList<Integer>(count);

    List<Integer> shuffledItems =  new ArrayList<Integer>(count);

    

    for (int i = 0 ; i < count ; i ++ ) {

      items.add(start + i);

    }

    

    while (items.size() > 0) {

      shuffledItems.add(items.remove((int)(1729 * Math.random()) % items.size()));

    }

    

    return shuffledItems;

  }

  

  public static List<String> shuffle(List<String> items) {

    

    List<Integer> shuffledItems = shuffle(0, items.size());

    List<String> shuffledStringItems =  new ArrayList<String>(items.size());

    

    for (int i = 0 ; i < shuffledItems.size() ; i ++ ) {

      shuffledStringItems.add(items.get(shuffledItems.get(i)));

    }

    

    return shuffledStringItems;

  }

}