PHP's strtotime() in Java

Question

strtotime() in PHP can do the following transformations:

Inputs:

 strtotime(’2004-02-12T15:19:21+00:00′); strtotime(’Thu, 21 Dec 2000 16:01:07 +0200′); strtotime(’Monday, January 1st’); strtotime(’tomorrow’); strtotime(’-1 week 2 days 4 hours 2 seconds’); 

Outputs:

 2004-02-12 07:02:21 2000-12-21 06:12:07 2009-01-01 12:01:00 2009-02-12 12:02:00 2009-02-06 09:02:41 

Is there an easy way to do this in java?

Yes, this is a duplicate. However, the original question was not answered. I typically need the ability to query dates from the past. I want to give the user the ability to say 'I want all events from "-1 week" to "now"'. It will make scripting these types of requests much easier.

Answer 1

I tried to implement a simple (static) class that emulates some of the patterns of PHP's strtotime. This class is designed to be open for modification (simply add a new Matcher via registerMatcher):

public final class strtotime {      private static final List<Matcher> matchers;      static {         matchers = new LinkedList<Matcher>();         matchers.add(new NowMatcher());         matchers.add(new TomorrowMatcher());         matchers.add(new DateFormatMatcher(new SimpleDateFormat("yyyy.MM.dd G 'at' HH:mm:ss z")));         matchers.add(new DateFormatMatcher(new SimpleDateFormat("EEE, d MMM yyyy HH:mm:ss Z")));         matchers.add(new DateFormatMatcher(new SimpleDateFormat("yyyy MM dd")));         // add as many format as you want      }      // not thread-safe     public static void registerMatcher(Matcher matcher) {         matchers.add(matcher);     }      public static interface Matcher {          public Date tryConvert(String input);     }      private static class DateFormatMatcher implements Matcher {          private final DateFormat dateFormat;          public DateFormatMatcher(DateFormat dateFormat) {             this.dateFormat = dateFormat;         }          public Date tryConvert(String input) {             try {                 return dateFormat.parse(input);             } catch (ParseException ex) {                 return null;             }         }     }      private static class NowMatcher implements Matcher {          private final Pattern now = Pattern.compile("now");          public Date tryConvert(String input) {             if (now.matcher(input).matches()) {                 return new Date();             } else {                 return null;             }         }     }      private static class TomorrowMatcher implements Matcher {          private final Pattern tomorrow = Pattern.compile("tomorrow");          public Date tryConvert(String input) {             if (tomorrow.matcher(input).matches()) {                 Calendar calendar = Calendar.getInstance();                 calendar.add(Calendar.DAY_OF_YEAR, +1);                 return calendar.getTime();             } else {                 return null;             }         }     }      public static Date strtotime(String input) {         for (Matcher matcher : matchers) {             Date date = matcher.tryConvert(input);              if (date != null) {                 return date;             }         }          return null;     }      private strtotime() {         throw new UnsupportedOperationException();     } } 

Usage

Basic usage:

 Date now = strtotime("now");  Date tomorrow = strtotime("tomorrow"); 

 Wed Aug 12 22:18:57 CEST 2009 Thu Aug 13 22:18:57 CEST 2009 

Extending

For example let's add days matcher:

strtotime.registerMatcher(new Matcher() {      private final Pattern days = Pattern.compile("[\\-\\+]?\\d+ days");      public Date tryConvert(String input) {          if (days.matcher(input).matches()) {             int d = Integer.parseInt(input.split(" ")[0]);             Calendar calendar = Calendar.getInstance();             calendar.add(Calendar.DAY_OF_YEAR, d);             return calendar.getTime();         }          return null;     } }); 

then you can write:

System.out.println(strtotime("3 days")); System.out.println(strtotime("-3 days")); 

(now is Wed Aug 12 22:18:57 CEST 2009)

 Sat Aug 15 22:18:57 CEST 2009 Sun Aug 09 22:18:57 CEST 2009