问题

I have to parse the following date

Fri Sep 30 18:31:00 GMT+04:00 2016

and it is not working with the following pattern:

new SimpleDateFormat("EEE MMM dd HH:mm:ss z YYYY", Locale.ENGLISH);

I get the following date as output: Fri Jan 01 18:31:00 GMT+04:00 2016.

Could you please tell me what I am doing wrong?

回答1:

It should be lower case "y":

EEE MMM dd HH:mm:ss z yyyy

Upper case "Y" means weekBasedYear:

a date can be created from a week-based-year, week-of-year and day-of-week

I guess mixing the week-based and absolute/era patterns just does not work well for parsing.

回答2:

tl;dr

OffsetDateTime
.parse
(
    "Fri Sep 30 18:31:00 GMT+04:00 2016" ,
    DateTimeFormatter.ofPattern( "EEE MMM d HH:mm:ss O uuuu" , Locale.US ) 
)
.toString()

2016-09-30T18:31+04:00

Avoid legacy classes

The other Answers are now outmoded. The terrible Date, Calendar, and SimpleDateFormat classes are now legacy, supplanted years ago by the modern java.time classes defined in JSR 310.

java.time

Your input string represents a date with time-of-day in the context of an offset-from-UTC. An offset is a number of hours ahead or behind of the baseline of UTC. For this kind of information, use OffsetDateTime class.

Note that an offset-from-UTC is not a time zone. A time zone is a history of the past, present, and future changes to the offset used by the people of a particular region.

The DateTimeFormatter class replaces SimpleDateFormat. The formatting codes are similar, but not exactly the same. So carefully study the Javadoc.

Notice that we pass a Locale. This specifies the human language and cultural norms to use in parsing the input, such as the name of the month, name of the day-of-week, the punctuation, the capitalization, and so on.

package work.basil.example.datetime;

import java.time.OffsetDateTime;
import java.time.format.DateTimeFormatter;
import java.util.Locale;

public class Parsing
{
    public static void main ( String[] args )
    {
        Parsing app = new Parsing();
        app.demo();
    }

    private void demo ( )
    {
        String input = "Fri Sep 30 18:31:00 GMT+04:00 2016";
        DateTimeFormatter f = DateTimeFormatter.ofPattern( "EEE MMM d HH:mm:ss O uuuu" , Locale.US );
        OffsetDateTime odt = OffsetDateTime.parse( input , f );

        System.out.println( "odt = " + odt );
    }
}

About java.time

The java.time framework is built into Java 8 and later. These classes supplant the troublesome old legacy date-time classes such as java.util.Date, Calendar, & SimpleDateFormat.

To learn more, see the Oracle Tutorial. And search Stack Overflow for many examples and explanations. Specification is JSR 310.

The Joda-Time project, now in maintenance mode, advises migration to the java.time classes.

You may exchange java.time objects directly with your database. Use a JDBC driver compliant with JDBC 4.2 or later. No need for strings, no need for java.sql.* classes. Hibernate 5 & JPA 2.2 support java.time.

Where to obtain the java.time classes?

Java SE 8, Java SE 9, Java SE 10, Java SE 11, and later - Part of the standard Java API with a bundled implementation.
- Java 9 brought some minor features and fixes.
Java SE 6 and Java SE 7
- Most of the java.time functionality is back-ported to Java 6 & 7 in ThreeTen-Backport.
Android
- Later versions of Android (26+) bundle implementations of the java.time classes.
- For earlier Android (<26), a process known as API desugaring brings a subset of the java.time functionality not originally built into Android.
  - If the desugaring does not offer what you need, the ThreeTenABP project adapts ThreeTen-Backport (mentioned above) to Android. See How to use ThreeTenABP….

回答3:

Below code is working fine

import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.Locale;

public class ParseDate {


public static void main(String[] args) {
    try {
        SimpleDateFormat parserSDF = new SimpleDateFormat("EEE MMM dd HH:mm:ss z yyyy", Locale.ENGLISH);
        Date date = parserSDF.parse("Fri Sep 30 18:31:00 GMT+04:00 2016");
        System.out.println("date: " + date.toString());
    } catch (ParseException ex) {
        ex.printStackTrace();
    }
}
}

来源：https://stackoverflow.com/questions/39785092/java-date-format-gmt-0400

标签

java

simpledateformat

datetime-parsing