Java ChronoLocalDateTime format()方法及示例

Java中ChronoLocalDateTime接口的 format() 方法使用指定的格式化器格式化这个日期时间。

语法

default String format(DateTimeFormatter formatter)

参数。该方法接受一个参数formatter，它指定了要使用的DateTimeFormatter，而不是null。

返回： 该函数返回 格式化的日期字符串 ，而不是null。

以下程序说明了ChronoLocalDateTime.format()方法。

程序1 :

// Java program to illustrate the format() method
  
import java.util.*;
import java.time.*;
import java.time.chrono.*;
import java.time.format.DateTimeFormatter;
  
public class GfG {
    public static void main(String[] args)
    {
        // Parses the date
        ChronoLocalDateTime dt1
            = LocalDateTime
                  .parse("2018-11-03T12:45:30");
  
        // Prints the date
        System.out.println("Original ChronoLocalDateTime: "
                           + 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 ChronoLocalDateTime: 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

程序2

// Program to illustrate the format() method
  
import java.util.*;
import java.time.*;
import java.time.chrono.*;
import java.time.format.DateTimeFormatter;
  
public class GfG {
    public static void main(String[] args)
    {
        // Parses the date
        ChronoLocalDateTime 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

参考资料: https://docs.oracle.com/javase/9/docs/api/java/time/chrono/ChronoLocalDateTime.html#format-java.time.format.DateTimeFormatter-