How to select duplicate values from a list in java?

Question

For example my list contains {4, 6, 6, 7, 7, 8} and I want final result = {6, 6, 7, 7}

One way is to loop through the list and eliminate unique values (4, 8 in this

Answer 1

Try this:

Inspired by this answer: https://stackoverflow.com/a/41262509/11256849

for (String s : yourList){
     if (indexOfNth(yourList, s, 2) != -1){
         Log.d(TAG, s);
      }
   }

Using this method:

public static  int indexOfNth(ArrayList list, T find, int nthOccurrence) {
        if (list == null || list.isEmpty()) return -1;
        int hitCount = 0;
        for (int index = 0; index < list.size(); index++) {
            if (list.get(index).equals(find)) {
                hitCount++;
            }
            if (hitCount == nthOccurrence) return index;
        }
        return -1;
    }