Reshuffling Elements in List

[Tiklu Mukherjee]

Hi,

I have a scenario where i want to accept an input from user, the input could be any combination of characters/integers. Now we have to Shuffle this input and use this Shuffled input for any particular use(Storing in DB/pass it as token value,etc) please find the below sample code, which is the work done by me to Shuffle the input.

import java.util.Scanner;

/**
Author : Abhijit Mukherjee
Date : 18-MAR-2013
Purpose : To Shuffle the given User Input String.
*/

public class Shuffle {

	public static void main(String args[])
	{

		 Scanner  LineInput=new Scanner(System.in);
		 
		 System.out.println("Please enter your input : "); /*-----------Enter the Input in any format(String/Integer/combination of String & Integer------------*/
	     
		 String userInput = LineInput.nextLine();
	     int inputLength = userInput.length();
		 StringBuilder inputBuilder = new StringBuilder();
		 
		 //Random Number generated in Range '0' to 'Maximum Userinput Length(inputLength)'
		 
		 for( int i =0; i<=inputLength; i++)
		 { 
			int r = (int) (Math.random() * ( inputLength - 0 ));
			inputBuilder.append(userInput.charAt(r));
		 }
		 
		 System.out.println("Original User Input String = "+userInput);
		 System.out.println("Shuffled user Input returns = "+inputBuilder);
	}
}

Till this point it is good enough to some extent , but i am looking for a different approach,i tried with Collection.shuffle() API and things go good in all way,
now i also want to Reshuffle back the Shuffled output from Collection.Shuffle() into original Input String.
To be precised,Collection.Shuffle() ,helps me to Shuffle elements in a LIST ,is there any JAVA API which can we used to Reshuffle it back(Here i dont want to use the Direct UserInput to retrieve the Original String).

Thanks for showing me the correct Way of Doing this,
Sincerely,
Abhijit

[Abhay Agarwal]

I am afraid , we do not have any such Java method to get your original String back from Re-shuffled output.
I think only way is that you have to save original data in your code

~abhay

[Tiklu Mukherjee]

Thanks Abhay,
On confirming that we don't have any such API to Re-Shuffle.

[Abhay Agarwal]

Or rather than using Java Collection shuffle() method, you can write your own implementation (method) for shuffling the List with your known pattern.

For example- you can decide to shuffle List elements based on any fixed & known pattern - Interchange elements present next to each other .

So if Original List is [A,B,C,D,E,F,G,H] then
and Shuffled List is [B,A,D,C,F,E,H,G]

Here , I have interchanged elements present at index 0 and 1. Then I have interchanged elements present at index 3 and 4. So on and so forth.

In this way, when we want to get original string back, we apply inverse of this Pattern. So, to get original string, again interchange adjacent elements.
So , you shall get[A,B,C,D,E,F,G,H] String back.

I have demonstrated a very simple Pattern to shuffle.
You can come up with your own Random Pattern.

Hope this will be helpful for you.
~ abhay

[Tiklu Mukherjee]

Thanks Abhay,

This do help with the scenario, i have also designed an alternative approach for this.

~Abhijit(Tiklu Mukherjee)
[e-mail]

[Tiklu Mukherjee]

Hi,
Developed an Approach for shuffling the user Input and reshuffling it back

import java.util.ArrayList;
import java.util.List;
import java.util.Scanner;

/**
Author : Abhijit Mukherjee
Date : 28-MAR-2013
Purpose : To Shuffle the given User Input String.
*/

public class Shuffle {

	public static void main(String args[])
	{

		 Scanner  LineInput=new Scanner(System.in);
		 List<Object> evenList = new ArrayList<Object>();
		 List<Object> oddList = new ArrayList<Object>();
		 
		 System.out.println("Please enter your input : "); /*-----------Enter the Input in any format(String/Integer/combination of String & Integer------------*/
//		 char userInput[] = LineInput.nextLine();
		 String  userInput[]  = new String [8];  
		 Scanner input = new Scanner(System.in);  
		 System.out.println("Enter the element");  
		    int total = 0 ;  
		    char a = 0;  
		 
		    for(int i = 0 ; i<= 7;i++){  
		    userInput[a] = LineInput.nextLine();  
		    a++;      
		    }
//		 char userInput[] = {'A','b','h','i','j','i','t'};
	         int inputLength = userInput.length;
		 StringBuilder inputBuilder = new StringBuilder();
		 
		 for(int i=0 ;i < inputLength; i++){
			 evenList.add(userInput[i]);
			 i++;	
		 }
		 for(int j=1;j<inputLength;j++){
			 oddList.add(userInput[j]);
			 j++;
		 }
		 System.out.println("even List = "+evenList.toString());
		 System.out.println("odd list = "+oddList);
		 
		 inputBuilder.append(oddList).append(evenList);
		 int oddPos=0;
		 String newInput = ""+inputBuilder.toString()+"";
		 System.out.println("New Shuffled Input = "+newInput);
		 
		 /*------------------Logic to reshuffl the input-------------*/
		 for(int pos=1;pos<userInput.length;pos++)
		 {
			evenList.add(pos, oddList.get(oddPos));
			 oddPos++;
			 pos++;
		 }
		 System.out.println("ReShuffled Input = "+evenList);
	}
}