Java date format

问题

Have String str "May 23 2011 12:20:00", want to convert it to date such this:

Date date = (new SimpleDateFormat("MMM dd yyyy HH:mm:ss")).parse(str);

It always gives me ParseException Unparsable date format: 'May 23 2011 12:20:00'.

Looked for similar issues, seems everything right.

What is wrong?

回答1:

You may need to additionally specify the Locale, when the default Locale of your VM is not an English one:

Date date = (new SimpleDateFormat("MMM dd yyyy HH:mm:ss", Locale.US)).parse(str);

回答2:

Works for me.!

回答3:

Try specifying locale while constructing SimpleDateFormat object.

回答4:

tl;dr

LocalDateTime.parse(
    "May 23 2011 12:20:00" , 
    DateTimeFormatter.ofPattern( "MMM d uuuu HH:mm:ss" , Locale.US )
)

Using java.time

The accepted Answer by Andreas Krueger is correct. You must specify a Locale to determine the human language used in translating the name of month. Best to make a habit of always specifying a locale in date-time work.

The modern approach avoids the troublesome old date-time classes, instead using their replacements, the java.time classes.

String input = "May 23 2011 12:20:00" ;

Define a formatting pattern to match the input using the DateTimeFormatter class.

The Locale determines (a) the human language for translation of name of day, name of month, and such, and (b) the cultural norms deciding issues of abbreviation, capitalization, punctuation, separators, and such.

Locale locale = Locale.US ;
DateTimeFormatter f = DateTimeFormatter.ofPattern( "MMM d uuuu HH:mm:ss" , locale );

Your input lacks any indication of time zone or offset-from-UTC. So we parse as a LocalDateTime.

LocalDateTime ldt = LocalDateTime.parse( input , f ) ;

ldt.toString(): 2011-05-23T12:20:00

---

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.

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

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

Where to obtain the java.time classes?

• Java SE 8, Java SE 9, and later
  • Built-in.
  • Part of the standard Java API with a bundled implementation.
  • Java 9 adds some minor features and fixes.
• Java SE 6 and Java SE 7
  • Much of the java.time functionality is back-ported to Java 6 & 7 in ThreeTen-Backport.
• Android
  • The ThreeTenABP project adapts ThreeTen-Backport (mentioned above) for Android specifically.
  • See How to use ThreeTenABP….

The ThreeTen-Extra project extends java.time with additional classes. This project is a proving ground for possible future additions to java.time. You may find some useful classes here such as Interval, YearWeek, YearQuarter, and more.

回答5:

Probably It's a problem with a tool you use. Take a look at:

Why am I getting a ParseException when using SimpleDateFormat to format a date and then parse it?

来源：https://stackoverflow.com/questions/6135658/java-date-format