Sort array of 0’s and 1’s

Array has 0’s and 1’s sort array like that all  0’s should come left and all 1’s should go right side.

import java.util.Objects;

public class SortZerosOnes {

 public static void sortArray(int arr[]) {
  Objects.nonNull(arr);
  if (arr.length < 2)
   return;

  int counter2 = arr.length - 1;

  for (int i = 0; i < counter2; i++) {
   if (arr[i] != 1 && arr[i] != 0)
    throw new IllegalArgumentException(
      "Array contains values other than 0, 1 : " + arr[i]);

   if (arr[i] == 1) {
    int temp = arr[i];
    arr[i] = arr[counter2];
    arr[counter2] = temp;
    i--;
    counter2--;
   }
  }
 }
}

Following is the junit test case for above class.

import static org.junit.Assert.assertTrue;

import java.util.Arrays;

import org.junit.Test;

public class SortZerosOnesTest {
 @Test
 public void test1() {
  int arr1[] = { 0, 1, 0, 1, 0, 1 };
  int arr2[] = { 0, 0, 1, 0, 1, 0, 1, 0, 0, 1 };
  int arr3[] = { 1, 0 };

  int expected1[] = { 0, 0, 0, 1, 1, 1 };
  int expected2[] = { 0, 0, 0, 0, 0, 0, 1, 1, 1, 1 };
  int expected3[] = { 0, 1 };

  SortZerosOnes.sortArray(arr1);
  SortZerosOnes.sortArray(arr2);
  SortZerosOnes.sortArray(arr3);

  assertTrue(Arrays.equals(arr1, expected1));
  assertTrue(Arrays.equals(arr2, expected2));
  assertTrue(Arrays.equals(arr3, expected3));
 }
}