无法将字符串解析为LocalDate（Java 8）

Question

My input is a String representation of a date in the format "01-07-2015" for July 1, 2015. I'm trying to parse this into a java.time.LocalDate variable:

final DateTimeFormatter DATE_FORMAT = DateTimeFormatter.ofPattern("dd-MM-YYYY");
final String input = "01-07-2015";
final LocalDate localDate = LocalDate.parse(input, DATE_FORMAT);

Based on the DateTimeFormatter JavaDoc , I would expect this to work. However, I'm greeted with a very friendly and helpful message:

Caused by: java.time.DateTimeException: Unable to obtain LocalDate from TemporalAccessor: {DayOfMonth=1, MonthOfYear=7, WeekBasedYear[WeekFields[MONDAY,4]]=2015},ISO of type java.time.format.Parsed

I don't really understand what this exception is telling me. Can anyone explain me what's going wrong?

Answer 1

For year you have to use the lowercase y:

final DateTimeFormatter DATE_FORMAT = DateTimeFormatter.ofPattern("dd-MM-yyyy");

Uppercase Y is used for weekyear. See the javadoc of DateTimeFormatter for more details.

Answer 2

The answer to the question is to use 'y' not 'Y'.

To explain the error message, lets decompose it:

Unable to obtain LocalDate from TemporalAccessor

This is saying that it cannot create a LocalDate (what was requested) from a TemporalAccessor (the low-level interface that provides hashmap-like access to the fields of date/time).

of type java.time.format.Parsed

This is saying that the object passed into the method was of type java.time.format.Parsed . This is the standard output type of parsing, and contains all the information that was parsed.

{DayOfMonth=1, MonthOfYear=7, WeekBasedYear[WeekFields[MONDAY,4]]=2015},ISO

This is the toString() form of the java.time.format.Parsed object that resulted from parsing. It is saying that four things were parsed:

• DayOfMonth=1 , the day-of-month parsed with value of 1
• MonthOfYear=7 , the month-of-year parsed with value of 7
• WeekBasedYear[WeekFields[MONDAY,4]]=2015 , the week-based-year parsed with value of 2015
• ISO , which is the ISO calendar system (a default value)

Since it is not possible to produce a LocalDate from the combination DayOfMonth + MonthOfYear + WeekBasedYear, an exception is thrown.

Note that the [WeekFields[MONDAY,4]] part refers to the fact that there are many different ways to define a week, in the US weeks start on Sunday, but in the ISO standard and the EU they start on Monday.