简化你的代码，提高生产力：这 10 个 Lambda 表达式必须掌握

List<String> list = Arrays.asList("apple", "banana", "orange");for (String fruit : list) {    System.out.println(fruit);}

List<String> list = Arrays.asList("apple", "banana", "orange");list.forEach(fruit -> System.out.println(fruit));

List<String> list = Arrays.asList("apple", "banana", "orange");Collections.sort(list, new Comparator<String>() {    public int compare(String s1, String s2) {        return s1.compareTo(s2);    }});

List<String> list = Arrays.asList("apple", "banana", "orange");Collections.sort(list, (s1, s2) -> s1.compareTo(s2));

List<String> list = Arrays.asList("apple", "banana", "orange");List<String> filteredList = new ArrayList<String>();for (String fruit : list) {    if (fruit.startsWith("a")) {        filteredList.add(fruit);    }}

List<String> list = Arrays.asList("apple", "banana", "orange");List<String> filteredList = list.stream().filter(fruit -> fruit.startsWith("a")).collect(Collectors.toList());

List<String> list = Arrays.asList("apple", "banana", "orange");List<Integer> lengths = new ArrayList<Integer>();for (String fruit : list) {    lengths.add(fruit.length());}

List<String> list = Arrays.asList("apple", "banana", "orange");List<Integer> lengths = list.stream().map(fruit -> fruit.length()).collect(Collectors.toList());

List<Integer> list = Arrays.asList(1, 2, 3, 4, 5);int sum = 0;for (int i : list) {    sum += i;}

List<Integer> list = Arrays.asList(1, 2, 3, 4, 5);int sum = list.stream().reduce(0, (a, b) -> a + b);

List<String> list = Arrays.asList("apple", "banana", "orange");Map<Integer, List<String>> grouped = new HashMap<Integer, List<String>>();for (String fruit : list) {    int length = fruit.length();    if (!grouped.containsKey(length)) {        grouped.put(length, new ArrayList<String>());    }    grouped.get(length).add(fruit);}

List<String> list = Arrays.asList("apple", "banana", "orange");Map<Integer, List<String>> grouped = list.stream().collect(Collectors.groupingBy(fruit -> fruit.length()));

public interface MyInterface {    public void doSomething(String input);}
MyInterface myObject = new MyInterface() {    public void doSomething(String input) {        System.out.println(input);    }};myObject.doSomething("Hello World");

MyInterface myObject = input -> System.out.println(input);myObject.doSomething("Hello World");

Thread thread = new Thread(new Runnable() {    public void run() {        System.out.println("Thread is running.");    }});thread.start();

Thread thread = new Thread(() -> System.out.println("Thread is running."));thread.start();

String str = "Hello World";if (str != null) {    System.out.println(str.toUpperCase());}

Optional<String> str = Optional.ofNullable("Hello World");str.map(String::toUpperCase).ifPresent(System.out::println);

List<String> list = Arrays.asList("apple", "banana", "orange");List<String> filteredList = new ArrayList<String>();for (String fruit : list) {    if (fruit.startsWith("a")) {        filteredList.add(fruit.toUpperCase());    }}Collections.sort(filteredList);

List<String> list = Arrays.asList("apple", "banana", "orange");List<String> filteredList = list.stream().filter(fruit -> fruit.startsWith("a")).map(String::toUpperCase).sorted().collect(Collectors.toList());