List<Dish> vegetarianMenu=menu.stream().filter(Dish::isVegetarian) .collect(toList());

List<Integer> numbers = Arrays.asList(1, 2, 1, 3, 3, 2, 4); 
numbers.stream().filter(i -> i % 2 == 0).distinct().forEach(System.out::println);

List<Dish> dishes = menu.stream() .filter(d -> d.getCalories() > 300).limit(3).collect(toList());

List<String> words = Arrays.asList("Java 8", "Lambdas", "In", "Action"); 
List<Integer> wordLengths = words.stream().map(String::length).collect(toList());

    List<String> words = Arrays.asList("Java 8", "Lambdas", "In", "Action");
    //map函數(shù)中每個(gè)字符串都被切割為字符串?dāng)?shù)組，返回一個(gè)字符串?dāng)?shù)組的流
    List<String[]> collect = words.stream()
        .map(word -> word.split(""))
        .distinct()
        .collect(toList());
    //Arrays.stram方法接受一個(gè)數(shù)組返回一個(gè)流
    String[] arrayOfWords = {"Goodbye", "World"};
    Stream<String> streamOfwords = Arrays.stream(arrayOfWords);

    //第一個(gè)map返回一個(gè)字符串流，流中的元素是一個(gè)個(gè)的字符串?dāng)?shù)組。
    //第二個(gè)map對每一個(gè)字符數(shù)組應(yīng)用Arrays.stream函數(shù)，所以每一個(gè)字     //符串?dāng)?shù)組映射為一個(gè)字符串流。
    List<Stream<String>> collect1 = words.stream()
        .map(word -> word.split(""))
        .map(v -> Arrays.stream(v))
        .distinct()
        .collect(toList());
    //第一個(gè)map返回一個(gè)字符串流，流中的元素是一個(gè)個(gè)的字符串?dāng)?shù)組。
    //flatMap方法把流中的每個(gè)字符串?dāng)?shù)組都換成一個(gè)流，然后連接它們成    //為一個(gè)流
    List<String> uniqueCharacters =
        words.stream()
            .map(w -> w.split(""))
            .flatMap(Arrays::stream)
            .distinct()
            .collect(Collectors.toList());

if(menu.stream().anyMatch(Dish::isVegetarian)){ 
 System.out.println("The menu is (somewhat) vegetarian friendly!!"); 
}

//是否所有元素都匹配
boolean isHealthy = menu.stream().allMatch(d -> d.getCalories() < 1000);
//是否所有元素都 不 匹配
boolean isHealthy = menu.stream().allMatch(d -> d.getCalories() < 1000);

Optional<Dish> dish = menu.stream().filter(Dish::isVegetarian).findAny();

List<Integer> someNumbers = Arrays.asList(1, 2, 3, 2, 5); 
//filter返回一個(gè)流，findfirst在該流中找第一個(gè)
Optional<Integer> firstSquareDivisibleByThree = 
 someNumbers.stream() 
 .filter(x -> x == 2) 
 .findFirst(); 

//求numbers中所有數(shù)值的集合
int product = numbers.stream().reduce(1, (a, b) -> a * b);