在Java中使用日期和时间函数的示例代码是什么？

在Java中使用日期和时间函数的示例代码如下：

1. 获取当前日期和时间：

import java.time.LocalDateTime;

public class Main {
    public static void main(String[] args) {
        LocalDateTime currentDateTime = LocalDateTime.now();
        System.out.println("Current Date and Time: " + currentDateTime);
    }
}

2. 格式化日期和时间：

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

public class Main {
    public static void main(String[] args) {
        LocalDateTime currentDateTime = LocalDateTime.now();
        DateTimeFormatter formatter = DateTimeFormatter.ofPattern("dd-MM-yyyy HH:mm:ss");
        String formattedDateTime = currentDateTime.format(formatter);
        System.out.println("Formatted Date and Time: " + formattedDateTime);
    }
}

3. 增加或减少日期和时间：

import java.time.LocalDateTime;
import java.time.temporal.ChronoUnit;

public class Main {
    public static void main(String[] args) {
        LocalDateTime currentDateTime = LocalDateTime.now();
        
        LocalDateTime newDateTime = currentDateTime.plusDays(5);
        System.out.println("Date and Time after adding 5 days: " + newDateTime);
        
        LocalDateTime anotherDateTime = currentDateTime.minusHours(2);
        System.out.println("Date and Time after subtracting 2 hours: " + anotherDateTime);
    }
}

4. 比较日期和时间：

import java.time.LocalDate;

public class Main {
    public static void main(String[] args) {
        LocalDate firstDate = LocalDate.of(2022, 1, 1);
        LocalDate secondDate = LocalDate.of(2023, 1, 1);
        
        if (firstDate.isBefore(secondDate)) {
            System.out.println(firstDate + " is before " + secondDate);
        } else if (firstDate.isAfter(secondDate)) {
            System.out.println(firstDate + " is after " + secondDate);
        } else {
            System.out.println(firstDate + " and " + secondDate + " are the same");
        }
    }
}

5. 计算两个日期之间的天数：

import java.time.LocalDate;
import java.time.temporal.ChronoUnit;

public class Main {
    public static void main(String[] args) {
        LocalDate firstDate = LocalDate.of(2022, 1, 1);
        LocalDate secondDate = LocalDate.of(2023, 1, 1);
        
        long daysBetween = ChronoUnit.DAYS.between(firstDate, secondDate);
        System.out.println("Days between " + firstDate + " and " + secondDate + ": " + daysBetween);
    }
}

这些示例代码演示了在Java中使用日期和时间函数的基本操作，可以根据自己的需求进行扩展和修改。