Pete has already given you the "correct" answer; now I shall give you the answer you want for homework.
Write a class called ArrayUtil or similar and in it implement a public static void swapPair(int array, int index1, int index2) method. Pass an array and the numbers of the two elements you want to swap to it. That will swap the two elements. Remember you need a temporary element in the method which will hold the original value while you swap.
Implement a public static void sort(int array) method which takes one of the better-known sorting algorithms. Several links to sorting algorithms available: see which of these is most useful: 123. Lots more available on Google.
Probably best to implement a public static void reverse(int array) method which uses the swap method you have already written to reverse the array; that is better than swapping < for > in the sort method.
Use the sort method then the reverse method. And lots of nice marks for you!