Please help with this Kth select method

/**

* Implement kth select.

*

* Use the provided random object to select your pivots.

* For example if you need a pivot between a (inclusive)

* and b (exclusive) where b > a, use the following code:

*

* int pivotIndex = r.nextInt(b - a) + a;

*

* It should be:

* in-place

*

* Have a worst case running time of:

* O(n^2)

*

* And a best case running time of:

* O(n)

*

* You may assume that the array doesn't contain any null elements.

*

* Make sure you code the algorithm as you have been taught it in class.

* There are several versions of this algorithm and you may not get full

* credit if you do not implement the one we have taught you!

*

* @throws IllegalArgumentException if the array or comparator or rand is

* null or k is not in the range of 1 to arr.length

* @param data type to sort

* @param k the index to retrieve data from + 1 (due to 0-indexing) if

* the array was sorted; the 'k' in "kth select"; e.g. if k ==

* 1, return the smallest element in the array

* @param arr the array that should be modified after the method

* is finished executing as needed

* @param comparator the Comparator used to compare the data in arr

* @param rand the Random object used to select pivots

* @return the kth smallest element

*/

public static T kthSelect(int k, T[] arr, Comparator comparator,

Random rand) {

}