code: public static Class<?> primitiveToWrapper(final Class<?> cls) {
          Class<?> convertedClass = cls;
          if (cls != null && cls.isPrimitive()) {
              convertedClass = primitiveWrapperMap.get(cls);
          }
          return convertedClass;
      }
docs: <p>Converts the specified primitive Class object to its corresponding
  wrapper Class object.</p>
  
  <p>NOTE: From v2.2, this method handles {@code Void.TYPE},
  returning {@code Void.TYPE}.</p>
  
  @param cls  the class to convert, may be null
  @return the wrapper class for {@code cls} or {@code cls} if
  {@code cls} is not a primitive. {@code null} if null input.
  @since 2.1