code: public static void compareAccumulatorTypes(Object name,
  			@SuppressWarnings("rawtypes") Class<? extends Accumulator> first,
  			@SuppressWarnings("rawtypes") Class<? extends Accumulator> second)
  			throws UnsupportedOperationException {
  		if (first != second) {
  			throw new UnsupportedOperationException("The accumulator object '" + name
  					+ "' was created with two different types: " + first + " and " + second);
  		}
  	}
docs: Compare both classes and throw {@link UnsupportedOperationException} if
  they differ