How to efficiently remove duplicates from an array without using Set

Question

I was asked to write my own implementation to remove duplicated values in an array. Here is what I have created. But after tests with 1,000,000 elements it took very long time to finish. Is there something that I can do to improve my algorithm or any bugs to remove ?

I need to write my own implementation - not to use Set, HashSet etc. Or any other tools such as iterators. Simply an array to remove duplicates.

public static int[] removeDuplicates(int[] arr) {      int end = arr.length;      for (int i = 0; i < end; i++) {         for (int j = i + 1; j < end; j++) {             if (arr[i] == arr[j]) {                                   int shiftLeft = j;                 for (int k = j+1; k < end; k++, shiftLeft++) {                     arr[shiftLeft] = arr[k];                 }                 end--;                 j--;             }         }     }      int[] whitelist = new int[end];     for(int i = 0; i < end; i++){         whitelist[i] = arr[i];     }     return whitelist; } 

Answer 1

If you are allowed to use Java 8 streams:

Arrays.stream(arr).distinct().toArray(); 

Answer 2

you can take the help of Set collection

int end = arr.length; Set<Integer> set = new HashSet<Integer>();  for(int i = 0; i < end; i++){   set.add(arr[i]); } 

now if you will iterate through this set, it will contain only unique values. Iterating code is like this :

Iterator it = set.iterator(); while(it.hasNext()) {   System.out.println(it.next()); }