static Class primitiveToBoxedType(Class type) {
  if (type == boolean.class) return Boolean.class;
  if (type == int.class) return Integer.class;
  if (type == long.class) return Long.class;
  if (type == float.class) return Float.class;
  if (type == short.class) return Short.class;
  if (type == char.class) return Character.class;
  if (type == byte.class) return Byte.class;
  if (type == double.class) return Double.class;
  null;
}

Began life as a copy of #1000961