Shuffle the elements of the array randomly
Naming


I would write array out instead of shortening it to arr (it's just two more letters), because it's more readable (but I do like that you are very consistent with your shortening).
is there a reason that you are using ii/jj instead of the more commonly used i/j?


Spacing

You should use a lot more spaces, because they make your code easier to read. 

I would at least add spaces after , and ;, before {, and around all = and &lt;.

You should also try to be more consistent with your spacing. For example, you have spaces around some =, but not all, and sometimes you write int [], other times int[].

Randomness

It seems that you implemented a variation of the fisher yates algorithm, which is actually not truly random, but biased:


  Similarly, always selecting j [rand.nextInt(arr.length) in your code] from the entire range of valid array indices on every iteration also produces a result which is biased, albeit less obviously so. 


You can go to Wikipedia to read the explanation. Implemented correctly, the swapArr method should probably look like this:

public static int[] swapArr(int[] arr) {
    Random random = new Random();
    for (int i = arr.length - 1; i &gt;= 0; i--) {
        int j = random.nextInt(i + 1);
        arr = swap(arr, i, j);
    }
    return arr;
}


Of course, Random only uses pseudorandom numbers anyways, so the slight bias might not be all that important.

Pass by Value

Strictly speaking, Java is pass-by-value, but you could still to this for example (because references of objects are passed, and thus changes to an object affect the object outside of the scope of a method):

public static void swap(int[] arr, int ii, int jj) {
    int temp = arr[ii];
    arr[ii] = arr[jj];
    arr[jj] = temp;
}


And then just call it like this:

swap(arr, i, j);


The same is true for swapArr. I think writing it this way is clearer (and also shorter), but it's probably a matter of taste.

Misc


I would split initArr into two methods: one that gets the user input, and one that creates the array (that way, it's easier to get the input from different places, for example hardcoded for testing).