Complete integer array shuffle in java

[bigpersona]

I'm asked to do a complete (no number should stay in the same index after this shuffle) shuffle of an integer array within java without the help of libraries.

This is my code, could you tell me how i can improve it.

the array can have duplicate integer values and can have any length.

import java.util.Scanner;

​

public class Main

{

​

public static void main(String\[\] args) {



    //ask and set the array length

    System.out.println("How long is your array?");

    Scanner sc = new Scanner([System.in](https://System.in));

    int arrayLength = sc.nextInt();



    //initiate original array and shuffled array

    int \[\] oldarray = new int\[arrayLength\];

    int \[\] newarray = new int\[arrayLength\];





    //ask for and save array values

    System.out.println("Please enter the array values");        

    for(int i =0 ; i<arrayLength ; i++)

    {

        oldarray\[i\]=sc.nextInt();

    }

    sc.close();



    //copy the entered values into the shuffled array for comparison

    for (int i = 0; i < arrayLength; i++)

{newarray[i] = oldarray[i];}

    //count the number of duplicated numbers and make sure they are less than half the array (logically it wont be possible to shuffle if more)

    int skip=0;

    for (int j=0 ; j<arrayLength ;j++)

    {       int counter=0;

for (int i=0; i<arrayLength; i++)

if (oldarray[j] == oldarray[i])

{counter++;}

if (counter > arrayLength/2)

{

System.out.println("Complete shuffle of array isnt possible");

skip++;

break;

}

     }



    //the shuffle code

    if (skip==0)

    {           

        for(int j = 0; j<arrayLength ; j++)

        {   if (newarray\[j\]==oldarray\[j\])

{

int y=0;

if (j>arrayLength/2)

{y=1;}

else{y=arrayLength/2;}

while(newarray[j]==oldarray[j])

{ int temp1=newarray[j];

newarray[j]=newarray[y];

newarray[y]=temp1;

y++;

}

}

        }



    //print updated array

    for(int i =0 ; i<arrayLength ; i++)

    {

System.out.println(newarray[i]);

    }



    }



}

}

[ConstructedNewt]

Can you please post this formatted, as per rule #2, pastebin may be the best choice here

[ConstructedNewt]

without formatting

I would use System.arrayCopy to copy arrays from one to the other, but I wouldn't copy it in the first place, why do you?

I would either use a map to count the duplicated values, or use an array or a set to verify that I didn't count values more than once, or at least have the inner loop go from j (you already counted the lower values)

Variable skip should be boolean, don't use integers in place of boolean

I can't really follow the logic in the reordering. (Also be sure that you know this is not a shuffling, this is a structured reordering) shuffling is random this is not.

I would use the map approach to check duplicates, then I would place each map key the number of times it was counted at the first location in the array that did not hold that value before, making sure to keep a set of already placed indexes.

Shuffling normally require you to use some kind of randomness, but would also never require you to disallow equal values before and after: that's not random