Java中的 LocalDateTime format() 方法

Java中LocalDateTime 类的format()方法使用指定的格式化程序格式化此日期时间。

句法：

public String format(DateTimeFormatter formatter)

参数：此方法接受一个参数格式化程序，它指定要使用的格式化程序，而不是 null。

返回：该函数返回格式化的日期字符串，并且不为空。

下面的程序说明了 LocalDateTime.format() 方法：

方案一：

// Java program to illustrate the format() method
  
import java.util.*;
import java.time.*;
import java.time.format.DateTimeFormatter;
  
public class GfG {
    public static void main(String[] args)
    {
        // Parses the date
        LocalDateTime dt1
            = LocalDateTime
                  .parse("2018-11-03T12:45:30");
  
        // Prints the date
        System.out.println("Original LocalDateTime: "
                           + dt1);
  
        // Display d1 in different formats
        // using format() method
        System.out.println("BASIC_ISO_DATE format: "
                           + (DateTimeFormatter.BASIC_ISO_DATE)
                                 .format(dt1));
        System.out.println("ISO_LOCAL_DATE format: "
                           + (DateTimeFormatter.ISO_LOCAL_DATE)
                                 .format(dt1));
        System.out.println("ISO_DATE format: "
                           + (DateTimeFormatter.ISO_DATE)
                                 .format(dt1));
        System.out.println("ISO_LOCAL_TIME format: "
                           + (DateTimeFormatter.ISO_LOCAL_TIME)
                                 .format(dt1));
          
    }
}

输出：

Original LocalDateTime: 2018-11-03T12:45:30
BASIC_ISO_DATE format: 20181103
ISO_LOCAL_DATE format: 2018-11-03
ISO_DATE format: 2018-11-03
ISO_LOCAL_TIME format: 12:45:30

方案二：

// Program to illustrate the format() method
  
import java.util.*;
import java.time.*;
import java.time.format.DateTimeFormatter;
  
public class GfG {
    public static void main(String[] args)
    {
        // Parses the date
        LocalDateTime dt1
            = LocalDateTime
                  .parse("2016-09-06T12:45:30");
  
        // Prints the date
        System.out.println(dt1);
  
        // Display d1 in different formats
        // using format() method
        System.out.println("ISO_TIME format: "
                           + (DateTimeFormatter.ISO_TIME)
                                 .format(dt1));
        System.out.println("ISO_LOCAL_DATE_TIME format: "
                           + (DateTimeFormatter.ISO_LOCAL_DATE_TIME)
                                 .format(dt1));
        System.out.println("ISO_DATE_TIME format: "
                           + (DateTimeFormatter.ISO_DATE_TIME)
                                 .format(dt1));
        System.out.println("ISO_ORDINAL_DATE format: "
                           + (DateTimeFormatter.ISO_ORDINAL_DATE)
                                 .format(dt1));
        System.out.println("ISO_WEEK_DATE format: "
                           + (DateTimeFormatter.ISO_WEEK_DATE)
                                 .format(dt1));
    }
}

输出：

2016-09-06T12:45:30
ISO_TIME format: 12:45:30
ISO_LOCAL_DATE_TIME format: 2016-09-06T12:45:30
ISO_DATE_TIME format: 2016-09-06T12:45:30
ISO_ORDINAL_DATE format: 2016-250
ISO_WEEK_DATE format: 2016-W36-2

参考： https: Java Java.time.format.DateTimeFormatter)