Convert String to Calendar Object in Java

Question

I am new to Java  usually work with PHP   I am trying to convert this string      Mon Mar 14 16 02 37 GMT 2011   Into a Calendar Object so that I can easily pull the Year and Month like this   String yearAndMonth   cal get Calendar YEAR  cal get Calendar MONTH     Would it be a bad idea to parse it manually  Using a substring method   Any advice would help thanks

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No new Calendar needs to be created  SimpleDateFormat already uses a Calendar underneath   SimpleDateFormat sdf   new SimpleDateFormat  EEE MMM dd HH mm ss z yyyy   Locale EN US   Date date   sdf parse  Mon Mar 14 16 02 37 GMT 2011       all done Calendar cal   sdf getCalendar       I can t comment yet  that s why I created a new answer

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Parse a time with timezone  Z in pattern is for time zone  String aTime    2017-10-25T11 39 00 09 00   SimpleDateFormat sdf   new SimpleDateFormat  yyyy-MM-dd T HH mm ssZ   Locale getDefault     try       Calendar cal   Calendar getInstance        cal setTime sdf parse aTime        Log i TAG   time       cal getTimeInMillis        catch  ParseException e        e printStackTrace        Output  it will return the UTC time  1508899140000     If we don t set the time zone in pattern like yyyy-MM-dd T HH mm ss  SimpleDateFormat will use the time zone which have set in Setting

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Well  I think it would be a bad idea to replicate the code which is already present in classes like SimpleDateFormat   On the other hand  personally I d suggest avoiding Calendar and Date entirely if you can  and using Joda Time instead  as a far better designed date and time API  For example  you need to be aware that SimpleDateFormat is not thread-safe  so you either need thread-locals  synchronization  or a new instance each time you use it  Joda parsers and formatters are thread-safe

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Calendar cal   Calendar getInstance    SimpleDateFormat sdf   new SimpleDateFormat  EEE MMM dd HH mm ss z yyyy   Locale ENGLISH   cal setTime sdf parse  Mon Mar 14 16 02 37 GMT 2011       all done   note  set Locale according to your environment requirement    See Also   Javadoc

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tl dr  The modern approach uses the java time classes    YearMonth from      ZonedDateTime parse            Mon Mar 14 16 02 37 GMT 2011             DateTimeFormatter ofPattern   E MMM d HH mm ss z uuuu             toString        2011-03   Avoid legacy date-time classes  The modern way is with java time classes  The old date-time classes such as Calendar have proven to be poorly-designed  confusing  and troublesome   Define a custom formatter to match your string input   String input    Mon Mar 14 16 02 37 GMT 2011   DateTimeFormatter f   DateTimeFormatter ofPattern   E MMM d HH mm ss z uuuu       Parse as a ZonedDateTime   ZonedDateTime zdt   ZonedDateTime parse  input   f      You are interested in the year and month  The java time classes include YearMonth class for that purpose   YearMonth ym   YearMonth from  zdt      You can interrogate for the year and month numbers if needed   int year   ym getYear    int month   ym getMonthValue      But the toString method generates a string in standard ISO 8601 format   String output   ym toString      Put this all together   String input    Mon Mar 14 16 02 37 GMT 2011   DateTimeFormatter f   DateTimeFormatter ofPattern   E MMM d HH mm ss z uuuu     ZonedDateTime zdt   ZonedDateTime parse  input   f    YearMonth ym   YearMonth from  zdt    int year   ym getYear    int month   ym getMonthValue      Dump to console   System out println   input      input    System out println   zdt      zdt    System out println   ym      ym         input  Mon Mar 14 16 02 37 GMT 2011      zdt  2011-03-14T16 02 37Z GMT       ym  2011-03   Live code  See this code running in IdeOne com   Conversion  If you must have a Calendar object  you can convert to a GregorianCalendar using new methods added to the old classes   GregorianCalendar gc   GregorianCalendar from  zdt        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   amp  SimpleDateFormat   The Joda-Time project  now in maintenance mode  advises migration to java time   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 and 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 SE 7   Much of the java time functionality is back-ported to Java 6  amp  7 in ThreeTen-Backport   Android   The ThreeTenABP project adapts ThreeTen-Backport  mentioned above  for Android specifically  See How to use        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

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SimpleDateFormat is great  just note that HH is different from hh when working with hours  HH will return 24 hour based hours and hh will return 12 hour based hours   For example  the following will return 12 hour time   SimpleDateFormat sdf   new SimpleDateFormat  hh mm aa      While this will return 24 hour time   SimpleDateFormat sdf   new SimpleDateFormat  HH mm

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Yes it would be bad practice to parse it yourself   Take a look at SimpleDateFormat  it will turn the String into a Date and you can set the Date into a Calendar instance

User · Answer

Simple method   public Calendar stringToCalendar String date  String pattern  throws ParseException       String DEFAULT LOCALE NAME    pt       String DEFAULT COUNTRY    BR       Locale DEFAULT LOCALE   new Locale DEFAULT LOCALE NAME  DEFAULT COUNTRY       SimpleDateFormat format   new SimpleDateFormat pattern  LocaleUtils DEFAULT LOCALE       Date d   format parse date       Calendar c   getCalendar        c setTime d       return c

[java] Convert String to Calendar Object in Java

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