code: public static Class<?> getPrimitiveType(Class<?> wrapperType) {
          if (Boolean.class.equals(wrapperType)) {
              return Boolean.TYPE;
          } else if (Byte.class.equals(wrapperType)) {
              return Byte.TYPE;
          } else if (Character.class.equals(wrapperType)) {
              return Character.TYPE;
          } else if (Short.class.equals(wrapperType)) {
              return Short.TYPE;
          } else if (Integer.class.equals(wrapperType)) {
              return Integer.TYPE;
          } else if (Long.class.equals(wrapperType)) {
              return Long.TYPE;
          } else if (Float.class.equals(wrapperType)) {
              return Float.TYPE;
          } else if (Double.class.equals(wrapperType)) {
              return Double.TYPE;
          } else {
              return null;
          }
      }
docs: Returns the corresponding primitive type for the given primitive wrapper,
  or null if the type is not a primitive wrapper.
  
  @param wrapperType wrapperType
  @return the corresponding primitive type