Stream<T>

返回低热量的菜肴名称，并按照卡路里排序：

package com.ant.jdk8.chap04;

import java.util.Arrays;
import java.util.Comparator;
import java.util.List;

public class StreamDemo {
    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) );
        menu.stream()
                .filter(d->d.getCalories()<400)
                .sorted(Comparator.comparing(Dish::getCalories))
                .map(Dish::getName)
                .forEach(name-> System.out.println(name));
    }
}

按照类别对菜肴进行分组：

package com.ant.jdk8.chap04;

import java.util.Arrays;
import java.util.Comparator;
import java.util.List;
import java.util.Map;
import java.util.stream.Collectors;

public class StreamDemo {
    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<Type,List<Dish>> dishesByType = menu.stream().collect(Collectors.groupingBy(Dish::getType));
        System.out.println(dishesByType);
    }
}