Stream 应用示例 （2）

    private static Map<Boolean, Map<Dish.Type, List<Dish>>> vegetarianDishesByType() {
        return menu.stream().collect(partitioningBy(Dish::isVegetarian, groupingBy(Dish::getType)));
    }

    private static Object mostCaloricPartitionedByVegetarian() {
        return menu.stream().collect(
                partitioningBy(Dish::isVegetarian,
                        collectingAndThen(
                                maxBy(comparingInt(Dish::getCalories)),
                                Optional::get)));
    }