How to efficiently remove duplicates from an array without using Set

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());
}

If you are allowed to use Java 8 streams:

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

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