Question

In java, write method, shuffle, which accepts an array of int, creates a copy of the formal parameter, shuffles the copy, then returns the copied, shuffled array, leaving the formal parameter unchanged. Shuffling is a process of swapping each element of array with another element randomly chosen from the array.

For testing the shuffle method have main call shuffle, repeatedly having it shuffle its previously returned array until the returned (shuffled) array is identical (equal) to the original array that was first shuffled, So, your loop would contain a statement like the following:

shuffledArray = shuffle( shuffledArray );

To complete this part, you must write the method, areEqual, that returns true if the two arrays passed to it are equal, otherwise return false. main must count and display the number of shuffles needed to cause the original array to reappear. A sampling of these counts range from about 500,000 to over 10 million.

Answer 1

******Start of Program**********Copy the program from below****

package competition;

import java.util.Arrays;
import java.util.Random;
import java.util.concurrent.ThreadLocalRandom;

public class Shuffle {

   public static void main(String args[])
   {
   int[] initialArray = { 1, 2,3,4};
  
   System.out.print("ORIGINAL ARRAY: ");
   for (int i = 0; i < initialArray.length; i++)
   {
   System.out.print(initialArray[i] + " ");
   }
   System.out.println();
  
   int[] shuffledArray= shuffle(initialArray);//This will shuffle the array
  
   for(int a=0; a<=1000000000;a++)
       {
           if(Arrays.equals(initialArray, shuffledArray))//if shuffle array is equal to original array,print the value of a (shuffle count)
           {
                 
               System.out.print("Reappear Same Array After shuffle:");
               for (int i = 0; i < shuffledArray.length; i++)
               {
               System.out.print(shuffledArray[i] + " ");
               }
               System.out.println();
               System.out.println("the number of shuffles needed to cause the original array to reappear: "+a);
               break;
           }
           else
           {
                 
               shuffledArray= shuffle(initialArray);//if shuffle array is not equal to original array,again shuffle the array
           }
       }
  
   }
  
   static int[] shuffle(int[] ar)
   {
       int[] arrcopy = Arrays.copyOf(ar, ar.length);//creating a copy of the formal parameter, shuffles the copy, then returns.
   Random random = ThreadLocalRandom.current();
   for (int i = arrcopy.length - 1; i > 0; i--)
   {
   int index = random.nextInt(i + 1);
   int a = arrcopy[index];
   arrcopy[index] = arrcopy[i];
   arrcopy[i] = a;
   }
  
   return arrcopy;
   }

}

*****End of program************************************************

screen shot for program and some output sample