guava/src/com/google/common/collect/ObjectArrays.java
@CanIgnoreReturnValue
  static Object checkElementNotNull(Object element, int index) {
    if (element == null) {
      throw new NullPointerException("at index " + index);
    }
    return element;
  }
@CanIgnoreReturnValue
  static Object checkElementNotNull(Object element, int index) {
    if (element == null) {
      throw new NullPointerException("at index " + index);
    }
    return element;
  }
creation cost.