Remove duplicate elements from array

Remove duplicate elements from array and don’t use any data structure other than same array.

There may be number of ways to solve this problem. I am going to explain my own way.

Suppose array has elements like {2, 3, 4, 5, 2, 3, 4, 5}.  Following is the pseudo code.

startCounter = 0, endCounter = arrayLength-1 = 7

Step 1: Check the elements from startCounter+1 to endCounter, if any element matcher to arr[startCouter], swap that element to arr[endCounter]. Decrement endCounter.

Step 2: Repeat step 1, until startCounter < endCounter.

Step 3: Final result should be the elements in array from 0 to startCounter.

import java.util.Objects;

public class DuplicateRemover {
 /**
  * Return new array by removing duplicate elements
  * 
  * @return
  */
 public static int[] removeDuplicates(int arr[]) {
  int[] empty = new int[0];

  if (Objects.isNull(arr) || arr.length == 0) {
   return empty;
  }

  int endCounter = arr.length - 1;
  int startCounter = 0;

  for (startCounter = 0; startCounter <= endCounter; startCounter++) {
   for (int j = endCounter; j > startCounter; j--) {
    if (arr[j] == arr[startCounter]) {
     int temp = arr[endCounter];
     arr[endCounter] = arr[j];
     arr[j] = temp;
     endCounter--;
    }
   }
  }

  int b[] = new int[startCounter];
  for (int i = 0; i < startCounter; i++) {
   b[i] = arr[i];
  }

  return b;
 }

}

import org.junit.Assert;
import org.junit.Test;

public class DuplicateRemoverTest {

 @Test
 public void test() {
  int arr1[] = {};
  int arr2[] = { 1 };
  int arr3[] = { 1, 1 };
  int arr4[] = { 1, 1, 1 };
  int arr5[] = { 1, 2, 3, 4, 1, 2, 3, 4 };
  int arr6[] = { 1, 1, 2, 2, 3, 3, 4, 4 };

  int expected1[] = new int[0];
  int expected2[] = { 1 };
  int expected3[] = { 1 };
  int expected4[] = { 1 };
  int expected5[] = { 1, 2, 3, 4 };
  int expected6[] = { 1, 4, 2, 3 };

  Assert.assertArrayEquals(DuplicateRemover.removeDuplicates(arr1),
    expected1);
  Assert.assertArrayEquals(DuplicateRemover.removeDuplicates(arr2),
    expected2);
  Assert.assertArrayEquals(DuplicateRemover.removeDuplicates(arr3),
    expected3);
  Assert.assertArrayEquals(DuplicateRemover.removeDuplicates(arr4),
    expected4);
  Assert.assertArrayEquals(DuplicateRemover.removeDuplicates(arr5),
    expected5);
  Assert.assertArrayEquals(DuplicateRemover.removeDuplicates(arr6),
    expected6);
 }
}