code: @SuppressWarnings("unchecked")
    public static <T> Class<T> wrap(Class<T> type) {
      return (type.isPrimitive() || type == void.class) ? (Class<T>) PrimitiveToWrappers.get(type) : type;
    }
docs: Returns the corresponding wrapper type of {@code type} if it is a primitive
  type; otherwise returns {@code type} itself. Idempotent.
  
  <pre>
  wrap(int.class) == Integer.class
  wrap(Integer.class) == Integer.class
  wrap(String.class) == String.class
  </pre>