Concat两个字符串然后在Java中转换为日期

Question

I need to concat two strings together in Java and then format the string and make it a Date object.

The two strings that I have at the moment are 31/01/2012 and 20:00 and I want to do something like:

try {
  DateFormat formatter = new SimpleDateFormat("dd-MM-yyyy HH:mm");
  Date result = new Date();
  String tempDate = date + " " + f;
  result = formatter.parse(tempDate);
} catch (ParseException e) {
  ...etc
}

Can someone help me figure how to add the two strings together. Any help would be appreciated!

Answer 1

Your concatenation is fine. Yet it seems that your format is "dd/MM/yyyy HH:mm"

Answer 2

The code looks good. Just correct the format it should be

"dd/MM/yyyy HH:mm"

Answer 3

tl;dr

LocalDateTime.of( 
    LocalDate.parse( 
        "31/01/2012" , 
        DateTimeFormatter.ofPattern( "dd/MM/uuuu" ) 
    ) , 
    LocalTime.parse( "20:00" ) 
).atZone( ZoneId.of( "Africa/Tunis" ) ) 

2012-01-31T20:00+01:00[Africa/Tunis]

See this code run live at IdeOne.com .

Using java.time

You are using troublesome old date-time classes, now supplanted by the java.time classes.

You need not concatenate the strings. Parse each, one as a LocalDate and one as a LocalTime .

DateTimeFormatter fDate = DateTimeFormatter.ofPattern( "dd/MM/uuuu" ) ;
LocalDate ld = LocalDate.format( "31/01/2012" , fDate ) ;

LocalTime lt = LocalTime.parse( "20:00" ) ; // Built-in formatter handles standard ISO 8601 formats.

You can combine those two parts into LocalDateTime . A LocalDateTime has no concept of time zone nor offset-from-UTC .

LocalDateTime ldt = LocalDateTime.of( ld , lt ) ;

We have no indication of offset-from-UTC nor time zone. So we do not have a specific moment, on an idea about possible moments. For example, 8 PM comes much earlier in New Zealand ( Pacific/Auckland ) than it does in India ( Asia/Kolkata ), and comes hours later in France ( Europe/Paris ).

To determine a specific moment, we must put that LocalDateTime in the context of a time zone. Perhaps you intended that moment for UTC.

OffsetDateTime odt = ldt.atOffset( ZoneOffset.UTC ) ;

Or perhaps you meant that for Québec time.

Specify a proper time zone name in the format of continent/region , such as America/Montreal , Africa/Casablanca , or Pacific/Auckland . Never use the 3-4 letter abbreviation such as EST or IST as they are not true time zones, not standardized, and not even unique(!).

ZoneId z = ZoneId.of( "America/Montreal" ) ;
ZonedDateTime zdt = ldt.atZone( z ) ;

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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 .