code: public static Field makeAccessible(Field field) {
          if (field == null) {
              throw new IllegalArgumentException("Method argument field must not be null.");
          }
          if (isInaccessible(field) && !field.isAccessible()) {
              field.setAccessible(true);
          }
  
          return field;
      }
docs: Makes the {@link Field#setAccessible(boolean) accessible} only if it is not.
  @param field must not be <code>null</code>.
  @return the given field.