Java 8 Time API: how to parse string of format "MM.yyyy" to LocalDate

Question

I'm a bit discouraged with parsing dates in Java 8 Time API.

Previously I could easily write:

String date = "04.2013"; DateFormat df = new SimpleDateFormat("MM.yyyy"); Date d = df.parse(date);

But now if I use LocalDate and do it like this:

String date = "04.2013"; DateTimeFormatter formatter = DateTimeFormatter.ofPattern("MM.yyyy"); LocalDate ld = LocalDate.parse(date, formatter);

I receive an exception:

java.time.format.DateTimeParseException: Text '04' could not be parsed at index 0 java.time.format.DateTimeFormatter.parseResolved0(DateTimeFormatter.java:1948) java.time.format.DateTimeFormatter.parse(DateTimeFormatter.java:1850) java.time.LocalDate.parse(LocalDate.java:400) java.time.LocalDate.parse(LocalDate.java:385) com.luxoft.ath.controllers.JsonController.region(JsonController.java:38) sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) java.lang.reflect.Method.invoke(Method.java:483) org.springframework.web.method.support.InvocableHandlerMethod.invoke(InvocableHandlerMethod.java:215) org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:132) org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:104) org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandleMethod(RequestMappingHandlerAdapter.java:749) org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:689) org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:83) org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:938) org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:870) org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:961) org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:852) javax.servlet.http.HttpServlet.service(HttpServlet.java:617) org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:837) javax.servlet.http.HttpServlet.service(HttpServlet.java:723) org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:88) org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)

If I change string format to "yyyy-MM-dd" everything work perfectly, even without formatter:

String date = "2013-04-12"; LocalDate ld = LocalDate.parse(date);

So my question is: how to parse date in custom format using Java 8 Time API?

assylias · Accepted Answer · 2014-05-22 07:58:54Z

It makes sense: your input is not really a date because it does not have a day information. You should parse it as a YearMonth and use that result if you don't care about the day.

String date = "04.2013"; DateTimeFormatter formatter = DateTimeFormatter.ofPattern("MM.yyyy"); YearMonth ym = YearMonth.parse(date, formatter);

If you do need to apply a specific day, you can obtain a LocalDate from a YearMonth for example:

LocalDate ld = ym.atDay(1); //or LocalDate ld = ym.atEndOfMonth();

You can also use a TemporalAdjuster, for example, for the last day of the month*:

LocalDate ld = ym.atDay(1).with(lastDayOfMonth());

_{*with an import static java.time.temporal.TemporalAdjusters.lastDayOfMonth;}

That makes sense. If you are only representing a year and month (the exact date is irrelevant), then you only need to work with YearMonth. You don't need to convert it to LocalDate unlike pre-Java8 where we had to convert it to a default date of 1. :)
You can do LocalDate ld = ym.atEndOfMonth(); too.. Seriously, Java 8 Time API (JodaTime) is amazing :)

Meno Hochschild · Accepted Answer · 2014-05-26 07:48:28Z

Following alternative is probably not so nice but at least a successfully tested solution, too, so I mention it here for completeness and as supplement to the right answer of @assylias:

DateTimeFormatterBuilder builder = new DateTimeFormatterBuilder(); builder.parseDefaulting(ChronoField.DAY_OF_MONTH, 1); builder.append(DateTimeFormatter.ofPattern("MM.yyyy")); DateTimeFormatter dtf = builder.toFormatter(); String ym = "04.2013"; LocalDate date = LocalDate.parse(ym, dtf); System.out.println(date); // output: 2013-04-01

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