分区

package com.ant.jdk8.chap06;

import java.util.*;
import java.util.stream.Collectors;

public class DishPartitionDemo {
    public static void main(String[] args) {
        List<Dish> menu = Arrays.asList(
                new Dish("pork", false, 800, Type.MEAT),
                new Dish("beef", false, 700, Type.MEAT),
                new Dish("chicken", false, 400, Type.MEAT),
                new Dish("french fries", true, 530, Type.OTHER),
                new Dish("rice", true, 350, Type.OTHER),
                new Dish("season fruit", true, 120, Type.OTHER),
                new Dish("pizza", true, 550, Type.OTHER),
                new Dish("prawns", false, 300, Type.FISH),
                new Dish("salmon", false, 450, Type.FISH) );
        Map<Boolean,Map<Type,List<Dish>>> vegetarianDishesByType =
                menu.stream().collect(Collectors.partitioningBy(Dish::isVegetarian,
                        Collectors.groupingBy(Dish::getType)));
        System.out.println(vegetarianDishesByType);
    }
}

package com.ant.jdk8.chap06;

import java.util.*;
import java.util.stream.Collectors;

public class DishPartitionDemo {
    public static void main(String[] args) {
        List<Dish> menu = Arrays.asList(
                new Dish("pork", false, 800, Type.MEAT),
                new Dish("beef", false, 700, Type.MEAT),
                new Dish("chicken", false, 400, Type.MEAT),
                new Dish("french fries", true, 530, Type.OTHER),
                new Dish("rice", true, 350, Type.OTHER),
                new Dish("season fruit", true, 120, Type.OTHER),
                new Dish("pizza", true, 550, Type.OTHER),
                new Dish("prawns", false, 300, Type.FISH),
                new Dish("salmon", false, 450, Type.FISH) );
        Map<Boolean,Dish> mostCaloriesByVegetarian =
                menu.stream().collect(Collectors.partitioningBy(Dish::isVegetarian,
                        Collectors.collectingAndThen(
                                Collectors.maxBy(Comparator.comparingInt(Dish::getCalories)),Optional::get)));
        System.out.println(mostCaloriesByVegetarian);
    }
}