// 使用Lambda表達(dá)式遍歷集合
List<String> names = Arrays.asList("Alice", "Bob", "Charlie");
names.forEach(name -> System.out.println(name));

// 使用Lambda表達(dá)式排序集合
Comparator<String> stringLengthComparator = (s1, s2) -> s1.length() - s2.length();
names.sort(stringLengthComparator);

// 使用Stream API過(guò)濾和轉(zhuǎn)換集合元素
List<Integer> numbers = Arrays.asList(1, 2, 3, 4, 5, 6, 7, 8, 9, 10);
List<Integer> evenNumbers = numbers.stream()
        .filter(n -> n % 2 == 0) // 過(guò)濾出偶數(shù)
        .map(n -> n * 2) // 將每個(gè)元素乘以2
        .collect(Collectors.toList()); // 收集結(jié)果到列表中

// 使用Stream API對(duì)集合進(jìn)行排序
List<String> sortedNames = names.stream()
        .sorted(Comparator.reverseOrder()) // 降序排序
        .collect(Collectors.toList());

// 使用Optional避免空指針異常
Optional<String> optionalName = Optional.ofNullable(getName());
if (optionalName.isPresent()) {
    System.out.println("Hello, " + optionalName.get());
} else {
    System.out.println("Name is not available.");
}

// 使用Optional的orElse方法提供默認(rèn)值
String defaultName = optionalName.orElse("Default Name");
System.out.println("Default name: " + defaultName);

// 定義一個(gè)包含默認(rèn)方法的接口
public interface Greeter {
    default void greet() {
        System.out.println("Hello!");
    }
}

// 實(shí)現(xiàn)接口時(shí)可以選擇覆蓋默認(rèn)方法
public class FriendlyGreeter implements Greeter {
    @Override
    public void greet() {
        System.out.println("Hi there! Welcome!");
    }
}

// 也可以直接使用默認(rèn)方法
public class DefaultGreeter implements Greeter {
    // 沒有覆蓋默認(rèn)方法
}

public class Main {
    public static void main(String[] args) {
        FriendlyGreeter friendlyGreeter = new FriendlyGreeter();
        DefaultGreeter defaultGreeter = new DefaultGreeter();
        
        friendlyGreeter.greet(); // 輸出 "Hi there! Welcome!"
        defaultGreeter.greet();  // 輸出 "Hello!"
    }
}

import java.time.LocalDate;
import java.time.LocalDateTime;
import java.time.LocalTime;
import java.time.format.DateTimeFormatter;

public class DateTimeExample {
    public static void main(String[] args) {
        // 獲取當(dāng)前日期
        LocalDate currentDate = LocalDate.now();
        System.out.println("Current Date: " + currentDate);

        // 獲取當(dāng)前時(shí)間
        LocalTime currentTime = LocalTime.now();
        System.out.println("Current Time: " + currentTime);

        // 獲取當(dāng)前日期和時(shí)間
        LocalDateTime currentDateTime = LocalDateTime.now();
        System.out.println("Current Date and Time: " + currentDateTime);

        // 日期格式化
        DateTimeFormatter formatter = DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss");
        String formattedDateTime = currentDateTime.format(formatter);
        System.out.println("Formatted Date and Time: " + formattedDateTime);
    }
}

import java.util.stream.IntStream;

public class ParallelStreamsExample {
    public static void main(String[] args) {
        // 使用并行流計(jì)算前1000個(gè)奇數(shù)的和
        long sumOfOddNumbers = IntStream.iterate(1, i -> i + 2)
                .limit(1000)
                .parallel() // 轉(zhuǎn)換為并行流
                .sum();

        System.out.println("Sum of first 1000 odd numbers: " + sumOfOddNumbers);
    }
}

import java.util.ArrayList;
import java.util.List;

public class TypeInferenceExample {
    public static void main(String[] args) {
        // 使用鉆石操作符簡(jiǎn)化泛型實(shí)例化
        List<String> names = new ArrayList<>(); // 省略了尖括號(hào)中的類型參數(shù)
        names.add("Alice");
        names.add("Bob");
        names.add("Charlie");

        System.out.println(names);
    }
}