Java的.time.LocalDateTime类在Java中

Java 8 中引入的Java .time.LocalDateTime 类表示没有时区信息的本地日期时间对象。 Java的 LocalDateTime 类是一个不可变的日期时间对象，它表示yyyy-MM-dd-HH-mm-ss.zzz格式的日期。它实现了 ChronoLocalDateTime 接口并继承了对象类。

无论何时需要在没有时区引用的情况下表示时间，我们都可以使用 LocalDateTime 实例。例如，LocalDateTime 可用于在任何应用程序中启动批处理作业。作业将在服务器所在时区的固定时间运行。注意 LocalDateTime 实例是不可变的和线程的。

语法：类声明

public final class LocalDateTime 

extends Object 

implements Temporal, TemporalAdjuster, ChronoLocalDateTime, Serializable

该类的方法如下：

Method	Description
format()	It is used to format this date-time using the specified formatter.
get()	It is used to get the value of the specified field from this date-time as an int.
minusMinutes()	Returns a copy of this LocalDateTime with the specified number of minutes subtracted.
minusYears()	Returns a copy of this LocalDateTime with the specified number of years subtracted.
minusDays()	Returns a copy of this LocalDateTime with the specified number of days subtracted.
now()	It is used to obtain the current date-time from the system clock in the default time zone.
plusHours()	Returns a copy of this LocalDateTime with the specified number of hours added.
plusYears()	Returns a copy of this LocalDateTime with the specified number of years added.
plusDays()	Returns a copy of this LocalDateTime with the specified number of days added.

还有一些修改本地时间的方法如下  in LocalDateTime 可用于获取相对于现有 localdatetime 实例的新 localdatetime 实例。它们分别如下：

plusYears()、plusMonths()、plusDays()、plusHours()、plusMinutes()、plusSeconds()、plusNanos()、minusYears()、minusMonths()、minusDays()、minusHours()、minusMinutes()、minusSeconds() ), 减去Nanos()

示例 1：

Java

// Java Program to illustrate LocalDateTime Class of java.time package 
 
// Importing LocalDateTime class from java.time package
import java.time.LocalDateTime;
 
// Main class for LocalDateTime
public class GFG {
 
    // Main driver method
    public static void main(String[] args)
    {
        // Creating an object of LocalDateTime class
        // in the main() method
        LocalDateTime now = LocalDateTime.now();
 
        // Print statement
        System.out.println(now);
 
        // Adding 1 year, 1 month, 1 week and 1 day
        LocalDateTime localDateTime1 = now.plusYears(1)
                                           .plusMonths(1)
                                           .plusWeeks(1)
                                           .plusDays(1);
        // Print statement
        System.out.println(localDateTime1);
 
        // Subtracting 1 year, 1 month, 1 week and 1 day
        LocalDateTime localDateTime2
            = localDateTime1.minusYears(1)
                  .minusMonths(1)
                  .minusWeeks(1)
                  .minusDays(1);
        // Print statement
        System.out.println(localDateTime2);
 
        // Adding 1 hour, 1 minute, 1 second and 100
        // nanoseconds
        LocalDateTime localDateTime3
            = localDateTime2.plusHours(1)
                  .plusMinutes(1)
                  .plusSeconds(1)
                  .plusNanos(100);
        // Print statement
        System.out.println(localDateTime3);
 
        // Subtracting 1 hour, 1 minute, 1 second and 100
        // nanoseconds
        LocalDateTime localDateTime4
            = localDateTime3.minusHours(1)
                  .minusMinutes(1)
                  .minusSeconds(1)
                  .minusNanos(100);
        // Print statement
        System.out.println(localDateTime4);
    }
}

输出：

示例 2：创建指定时间

Java

// Java Program to illustrate LocalDateTime Class
// of java.time package by creating specific time
 
// Importing required classes from resp packages
import java.time.*;
import java.time.format.*;
 
// main class
class GFG {
 
    // Main driver method
    public static void main(String[] args)
    {
 
        // Milliseconds
        LocalDateTime localDateTime1 = LocalDateTime.of(
            2021, 04, 24, 14, 33, 48, 123456789);
        // Print statement
        System.out.println(localDateTime1);
 
        // Month
        LocalDateTime localDateTime2 = LocalDateTime.of(
            2021, Month.APRIL, 24, 14, 33, 48, 123456789);
        // Print statement
        System.out.println(localDateTime2);
 
        // Seconds
        LocalDateTime localDateTime3 = LocalDateTime.of(
            2021, Month.APRIL, 24, 14, 33, 48);
        // Print statement
        System.out.println(localDateTime3);
 
        // Minutes
        LocalDateTime localDateTime4 = LocalDateTime.of(
            2021, Month.APRIL, 24, 14, 33);
        // Print statement
        System.out.println(localDateTime4);
 
        // Local date + Local time
        LocalDate date = LocalDate.of(2021, 04, 24);
        LocalTime time = LocalTime.of(10, 34);
 
        LocalDateTime localDateTime5
            = LocalDateTime.of(date, time);
        // Print statement
        System.out.println(localDateTime5);
    }
}

输出：

示例 3 ：将 LocalDateTime 格式化为字符串

要将本地时间格式化为所需的字符串表示形式，请使用 LocalDateTime.format(DateTimeFormatter) 方法。

Java

// Java Program to illustrate LocalDateTime Class by
// Formatting LocalDateTime to string
 
// Importing all classes from java.time package
import java.time.LocalDateTime;
import java.time.format.*;
import java.util.*;
 
// Main class
class GFG {
 
    // Main driver method
    public static void main(String[] args)
    {
 
        // Creating an object of DateTimeFormatter class
        DateTimeFormatter formatter
            = DateTimeFormatter.ofPattern(
                "yyyy-MM-dd HH:mm:ss a");
 
        // Creating an object of LocalDateTime class
        // and getting local date and time using now()
        // method
        LocalDateTime now = LocalDateTime.now();
 
        // Formatting LocalDateTime to string
        String dateTimeString = now.format(formatter);
 
        // Print and Display
        System.out.println(dateTimeString);
    }
}

输出：

Note: In order to parse a string to LocalDateTime, convert time in a string to a local time instance, the LocalDateTime class has two overloaded parse() methods.

• parse(CharSequence text)
• parse(CharSequence text, DateTimeFormatter formatter)