MyComp

import java.util.ArrayList;
import java.util.Collections;
import java.util.Comparator;
import java.util.HashMap;
import java.util.HashSet;
import java.util.Set;

class MyClass {
  static HashMap<Integer, Integer> map;// = new HashMap<Integer,Integer>();

  public static void main(final String[] arrg) {
    final int[] arr = { 2, 5, 2, 8, 5, 6, 8, 8 };
    map = new HashMap<Integer, Integer>();
    final Set<Integer> set = new HashSet<>();
    for (int i = 0; i < arr.length; i++) {
      if (map.get(arr[i]) == null) {
        map.put(arr[i], 1);
      } else {
        int count = map.get(arr[i]);
        map.put(arr[i], ++count);
      }

      set.add(arr[i]);
    }
    final ArrayList<Integer> list = new ArrayList<Integer>(set);
    Collections.sort(list, new MyComp());
    System.out.println(list);
  }

  static class MyComp implements Comparator<Integer> {
    @Override
    public int compare(final Integer o1, final Integer o2) {
      final int count1 = map.get(o1);
      final int count2 = map.get(o2);

      if (count1 > count2) {
        return -1;
      } else if (count1 < count2) {
        return 1;
      } else {
        return 0;
      }
    }
  }
}