我是 Java 8 的新手，流式收集器試圖了解兩者之間的基本區別是什么？因為這兩個代碼都產生了相同的結果。一個使用return groupingBy(classifier, toList());并返回 groupingBy(classifier, HashMap::new,downstream);這是代碼public class Grouping {    enum CaloricLevel { DIET, NORMAL, FAT };    public static void main(String[] args) {        System.out.println("Dishes grouped by type: " + groupDishesByType());        System.out.println("Dish names grouped by type: " + groupDishNamesByType());    }    private static Map<Type, List<Dish>> groupDishesByType() {        return Dish.menu.stream().collect(groupingBy(Dish::getType));    }    private static Map<Type, List<String>> groupDishNamesByType() {        return Dish.menu.stream().collect(groupingBy(Dish::getType, mapping(Dish::getName, toList())));    }}輸出：Dishes grouped by type: {MEAT=[pork, beef, chicken], OTHER=[french fries, rice, season fruit, pizza], FISH=[prawns, salmon]}Dish names grouped by type: {MEAT=[pork, beef, chicken], OTHER=[french fries, rice, season fruit, pizza], FISH=[prawns, salmon]}菜.javapublic class Dish {    private final String name;    private final boolean vegetarian;    private final int calories;    private final Type type;    public Dish(String name, boolean vegetarian, int calories, Type type) {        this.name = name;        this.vegetarian = vegetarian;        this.calories = calories;        this.type = type;    }    public String getName() {        return name;    }    public boolean isVegetarian() {        return vegetarian;    }    public int getCalories() {        return calories;    }    public Type getType() {        return type;    }    public enum Type {        MEAT, FISH, OTHER    }    @Override    public String toString() {        return name;    }}