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