Question

Java ((without using array))

3. Write a program that reads a 7-digit number and then shuffles its digits randon Sample run: Please enter a number 123456 Wrong too small! Sample run: Please enter a number: 1234567 The shuffled number is: 4356271 Sample run: Please enter a number 1000001 The shuffled number is: 0100100

Answer 1

import java.util.concurrent.ThreadLocalRandom;
import java.util.Scanner;
   public class ShuffleNumber {
        public static void main(String[] args) {
            ShuffleNumber sn = new ShuffleNumber(); // Create shuffle object
            Scanner reader = new Scanner(System.in); // Reading from System.in
            System.out.print("Please enter a number: ");
            String number = reader.nextLine(); //Read input from user
            if(number.length() < 7)
            {   //If input number length is less than 7 then return error
                System.out.println("Wrong too small !");
                return;
            }
            else if(number.length() > 7)
            {   //If input number length is greater than 7 then return error
                System.out.println("Wrong too large !");
                return;
            }
            String shuffled = sn.shuffle(number); //Call shuffle function
            System.out.println("The Shuffled number is: "+shuffled); // Display the result
        }
  
         private String shuffle(String number) {
            String shuffledNumber = number; // start with original number
            int numSize = number.length(); // Get the number length
            int shuffleCount = 7; // Shuffle randomly 7 times
            for(int i=0;i<shuffleCount;i++) {
                //swap letters in two indexes
                int pos1 = ThreadLocalRandom.current().nextInt(0, numSize); //Get first random position
                int pos2 = ThreadLocalRandom.current().nextInt(0, numSize); //Get second random position
                shuffledNumber = swapCharacters(shuffledNumber,pos1,pos2); //Get the result shuffled number by swapping characters
            }
            return shuffledNumber; //Return the shuffled number
        }
  
      private String swapCharacters(String shuffledNumber, int pos1, int pos2) {;
            //If both positions are same or position1 is more than position2 or position 2 is the last digit, then return without doing any changes
            if(pos1 > pos2 || pos1 == pos2 || pos2 >= shuffledNumber.length()-1)
                return shuffledNumber;
            String s1 = shuffledNumber.substring(0, pos1); //Else get number upto first position
            String s2 = shuffledNumber.substring(pos1+1, pos2); //Get number in between pos1 and pos2
            String s3 = shuffledNumber.substring(pos2+1); //Get number from pos2 to end
            return s1+shuffledNumber.charAt(pos2)+s2+shuffledNumber.charAt(pos1)+s3; // Add all strings and swap pos1 with pos2
        }
   }

Please enter a number: 1234567 The Shuffled number is: 5472136 Please enter a number: 1900001 The Shuffled number is: 0100001

Note: Please note that the shuffle is being done randomly. So each time you can get different output even if the input is same. And I have added check to do shuffle only for 7 digits number. As you want number 0 to be shuffled also, so I am doing operations on string and didn't use array anywhere in program. Thanks. Ping me back for any doubts.