### Question:
SingleNumber { public int singleNumber3(int[] nums) { Set<Integer> set = new HashSet<>(nums.length); for (int num : nums) { if(set.contains(num)){ set.remove(num); }else{ set.add(num); } } return set.iterator().next(); }  int singleNumber(int[] nums); int singleNumber2(int[] nums); int singleNumber3(int[] nums);  }### Answer:
@Test void go3() { SingleNumber singleNumber = new SingleNumber(); for (int i = 0; i < cases.size(); i++) { assertEquals((int)results.get(i), singleNumber.singleNumber3(cases.get(i))); } }