Java函数式编程中高阶函数的使用场景有哪些？

Function<String, Integer> stringToInt = Integer::parseInt;
Function<Integer, Double> intToDouble = Double::valueOf;

Function<String, Double> stringToDouble = stringToInt.compose(intToDouble);

// 使用
String input = "123";
double result = stringToDouble.apply(input);

Function<Integer, Function<Integer, Integer>> add = x -> y -> x + y;

// 使用
int result = add.apply(10).apply(5); // 15

Supplier<Double> lazyPi = () -> {
    double sum = 0;
    for (int i = 0; i < 1000000; i++) {
        sum += Math.pow(-1, i) / (2 * i + 1);
    }
    return sum * 4;
};

// 仅当需要时才计算 Pi 值
double pi = lazyPi.get();

List<String> names = List.of("John", "Mary", "Bob", "Alice");

String longestName = names.stream()
    .filter(name -> name.length() > 4)
    .max(Comparator.comparing(String::length))
    .get();

// GUI 按钮事件处理程序
Button button = new Button("Click me");
button.setOnAction(e -> System.out.println("Button clicked!"));