How to find the permutation of a sort in Java

Let's assume your elements are stored in an array.

final int[] arr = // elements you want
List<Integer> indices = new ArrayList<Integer>(arr.length);
for (int i = 0; i < arr.length; i++) {
  indices.add(i);
}
Comparator<Integer> comparator = new Comparator<Integer>() {
  public int compare(Integer i, Integer j) {
    return Integer.compare(arr[i], arr[j]);
  }
}
Collections.sort(indices, comparator);

Now indices contains the indices of the array, in their sorted order. You can convert that back to an int[] with a straightforward enough for loop.

import java.util.*;
public class Testing{
   public static void main(String[] args){
       int[] arr = {3, 2, 4, 6, 5};
       TreeMap map = new TreeMap();
       for(int i = 0; i < arr.length; i++){
            map.put(arr[i], i);
       }
       System.out.println(Arrays.toString(map.values().toArray()));
   }
}