I need help with the following Java code

/**

* Simple sorting algorithms' implementations. Note that it is

* fine to create private helper methods inside this class.

* However, you are not allowed to have an instance or class

* variables.

*

* @author

*/

public class SimpleSorts

{

/**

* Sorts entries of array "arr" using recursive selection

* sort algorithm in nondecreasing order. You can assume

* that array won't be null and will have at least 2 elements.

*/

public static void selectionSortRec(int[] arr)

{

}

/**

* Sorts entries of array "arr" using recursive insertion

* sort algorithm in nondecreasing order. You can assume

* that array won't be null and will have at least 2 elements.

*/

public static void insertionSortRec(int[] arr)

{

}

/**

* A bubble sort can sort an array of n entries into nondecreasing order

* by making n-1 passes through the array. On each pass, it compares adjacent

* entries and swaps them if they are out of order. For example, on the first

* pass, it compares the first and second entries, then the second and third

* entries, and so on. At the end of the first pass, the largest entry is in

* its proper position at the end of the array. We say that it has bubbled to

* its correct spot. Each subsequent pass ignores the entries at the end of the

* array, since they are sorted and are larger than any of the remaining entries.

* Thus, each pass makes one fewer comparison than the previous pass.

*

* Here is an example of a bubble sort.

* (Numbers in parentheses represent sorted subarray.)

*

* Original array: 8 2 6 4 9 7 1

* After pass 1 : 2 6 4 8 7 1 (9)

* After pass 2 : 2 4 6 7 1 (8 9)

* After pass 3 : 2 4 6 1 (7 8 9)

* After pass 4 : 2 4 1 (6 7 8 9)

* After pass 5 : 2 1 (4 6 7 8 9)

* After pass 6 : 1 (2 4 6 7 8 9)

*

* Here is the detail of pass 1.

* (Square brackets indicate currently compared entries of array.)

*

* Original array: 8 2 6 4 9 7 1

* Step 1 : [8 2] 6 4 9 7 1 compare 1st and 2nd; swap

* Step 2 : 2 [8 6] 4 9 7 1 compare 2nd and 3rd; swap

* Step 3 : 2 6 [8 4] 9 7 1 compare 3rd and 4th; swap

* Step 4 : 2 6 4 [8 9] 7 1 compare 4th and 5th; no swap

* Step 5 : 2 6 4 8 [9 7] 1 compare 5th and 6th; swap

* Step 6 : 2 6 4 8 7 [9 1] compare 6th and 7th; swap

* Step 7 : 2 6 4 8 7 1 9 steps repeated at next pass.

*

* For more info check: https://en.wikipedia.org/wiki/Bubble_sort

* Note: It is OK to reuse their pseudocode ideas.

*/

/**

* Sorts entries of array "arr" using iterative bubble

* sort algorithm in nondecreasing order. You can assume

* that array won't be null and will have at least 2 elements.

*/

public static void bubbleSortItr(int[] arr)

{

}

/**

* Sorts entries of array "arr" using recursive bubble

* sort algorithm in nondecreasing order. You can assume

* that array won't be null and will have at least 2 elements.

*/

public static void bubbleSortRec(int[] arr)

{

}

}