@FunctionalInterface
public interface BiFunction<T, U, R> {
    R apply(T t, U u);
}

// 示例1：簡(jiǎn)單的數(shù)值計(jì)算
BiFunction<Integer, Integer, Integer> add = (a, b) -> a + b;
System.out.println(add.apply(5, 3)); // 輸出：8
// 示例2：字符串拼接
BiFunction<String, String, String> concat = (str1, str2) -> str1 + str2;
System.out.println(concat.apply("Hello, ", "World!")); // 輸出：Hello, World!
// 示例3：對(duì)象屬性計(jì)算
class Person {
    private String name;
    private int age;
    public Person(String name, int age) {
        this.name = name;
        this.age = age;
    }
    @Override
    public String toString() {
        return "Person{name='" + name + "', age=" + age + "}";
    }
}
// 創(chuàng)建Person對(duì)象的BiFunction
BiFunction<String, Integer, Person> personCreator = Person::new;
Person person = personCreator.apply("Alice", 30);
System.out.println(person); // 輸出：Person{name='Alice', age=30}

// andThen示例：先相加再乘以2
BiFunction<Integer, Integer, Integer> add = (a, b) -> a + b;
Function<Integer, Integer> doubleValue = x -> x * 2;
BiFunction<Integer, Integer, Integer> addThenDouble = add.andThen(doubleValue);
System.out.println(addThenDouble.apply(5, 3)); // 輸出：16
// compose示例：先將輸入乘以2再相加
Function<Integer, Integer> doubleFirst = x -> x * 2;
BiFunction<Integer, Integer, Integer> doubleFirstThenAdd = add.compose(doubleFirst);
System.out.println(doubleFirstThenAdd.apply(5, 3)); // 輸出：13（5*2 + 3 = 13）

@FunctionalInterface
public interface BinaryOperator<T> extends BiFunction<T, T, T> {
    // 繼承自BiFunction的apply方法
    T apply(T t, T u);
    // 靜態(tài)工廠方法
    static <T> BinaryOperator<T> minBy(Comparator<? super T> comparator) {
        // 實(shí)現(xiàn)略
    }
    static <T> BinaryOperator<T> maxBy(Comparator<? super T> comparator) {
        // 實(shí)現(xiàn)略
    }
}

// 示例1：數(shù)值運(yùn)算
BinaryOperator<Integer> add = (a, b) -> a + b;
System.out.println(add.apply(5, 3)); // 輸出：8
// 示例2：字符串最長(zhǎng)拼接（返回較長(zhǎng)的字符串）
BinaryOperator<String> longestString = (str1, str2) -> 
    str1.length() > str2.length() ? str1 : str2;
System.out.println(longestString.apply("Hello", "World!")); // 輸出：World!
// 示例3：使用靜態(tài)工廠方法
List<Integer> numbers = Arrays.asList(10, 5, 8, 15, 3);
// 使用maxBy找到最大值
BinaryOperator<Integer> max = BinaryOperator.maxBy(Comparator.naturalOrder());
int result = numbers.stream()
        .reduce(0, max); // 初始值為0，可能需要調(diào)整邏輯
System.out.println(result); // 輸出：15

List<Integer> numbers = Arrays.asList(1, 2, 3, 4, 5);
// 計(jì)算總和（使用Lambda表達(dá)式）
int sum = numbers.stream()
        .reduce(0, (a, b) -> a + b);
System.out.println("總和：" + sum); // 輸出：15
// 計(jì)算總和（使用BinaryOperator）
BinaryOperator<Integer> addOperator = Integer::sum;
int sum2 = numbers.stream()
        .reduce(0, addOperator);
System.out.println("總和：" + sum2); // 輸出：15
// 尋找最大值
Integer max = numbers.stream()
        .reduce(Integer::max)
        .orElse(0);
System.out.println("最大值：" + max); // 輸出：5

// 將兩個(gè)不同類型的數(shù)據(jù)轉(zhuǎn)換為新類型
BiFunction<String, Integer, Map<String, Object>> userMapper = (name, age) -> {
    Map<String, Object> user = new HashMap<>();
    user.put("name", name);
    user.put("age", age);
    return user;
};
Map<String, Object> user = userMapper.apply("Bob", 25);
System.out.println(user); // 輸出：{name=Bob, age=25}

List<String> words = Arrays.asList("Java", "is", "powerful");
// 使用BinaryOperator連接字符串
String result = words.stream()
        .reduce("", (a, b) -> a + (a.isEmpty() ? "" : " ") + b);
System.out.println(result); // 輸出：Java is powerful
// 更簡(jiǎn)潔的寫法
String result2 = words.stream()
        .reduce("", String::concat);
System.out.println(result2); // 輸出：Javaispowerful（無(wú)空格）

// 定義多個(gè)BiFunction并組合使用
BiFunction<Integer, Integer, Integer> add = (a, b) -> a + b;
BiFunction<Integer, Integer, Integer> multiply = (a, b) -> a * b;
// 先相加再相乘：(a + b) * c
BiFunction<Integer, Integer, Integer> addThenMultiply = add.andThen(b -> multiply.apply(b, 2));
System.out.println(addThenMultiply.apply(3, 4)); // 輸出：14（(3+4)*2=14）

class Product {
    private String name;
    private double price;
    private int quantity;
    // 構(gòu)造器、getter和setter略
    @Override
    public String toString() {
        return "Product{" +
                "name='" + name + "', " +
                "price=" + price + ", " +
                "quantity=" + quantity +
                '}';
    }
}
// 計(jì)算產(chǎn)品總價(jià)值的BinaryOperator
BinaryOperator<Product> calculateTotalValue = (p1, p2) -> {
    double totalPrice = p1.getPrice() * p1.getQuantity() + p2.getPrice() * p2.getQuantity();
    return new Product("Total", totalPrice, 1); // 簡(jiǎn)化處理
};
Product product1 = new Product("Laptop", 899.99, 2);
Product product2 = new Product("Phone", 599.99, 3);
Product total = calculateTotalValue.apply(product1, product2);
System.out.println(total); // 輸出總價(jià)值計(jì)算結(jié)果