Why do I have NullPointerException in my sort implementation?

Question

I\'m working on my assignment and I am suppose to create a sort method for my array. However, I\'m getting a null pointer error in my sort method and I\'m not sure why. This is

Answer 1

See if any elements of setArray are null. Arrays.sort() requires that each element of the array being sorted has to be non-null: "All elements in the array must implement the Comparable interface."