Java: Convert Min Heap to Max Heap

Problem Statement:

Given an array representation of min Heap, convert it to max Heap.

Input:

arr[] = {3, 5, 9, 6, 8, 20, 10, 12, 18, 9}
3
/ \
5 9
/ \ / \
6 8 20 10
/ \ /
12 18 9

Output:

arr[] = {20, 18, 10, 12, 9, 9, 3, 5, 6, 8}
  20
  / \
 18  10
/ \  / \
12 9 9 3
/ \ /
5 6 8