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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:
1 2 3. 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!