Unknown pattern character 'x', when using SimpleDateFormat

Question

Im trying to format a Date to String using SimpleDateFormat, and the pattern im using is this one

"yyyy-MM-dd'T'HH:mm:ss.SSSxxx"

but when reach this line

SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ss.SSSxxx");

i get the following exception:

java.lang.IllegalArgumentException: Unknown pattern character 'x' at java.text.SimpleDateFormat.validatePatternCharacter(SimpleDateFormat.java:323) at java.text.SimpleDateFormat.validatePattern(SimpleDateFormat.java:312) at java.text.SimpleDateFormat.(SimpleDateFormat.java:365) at java.text.SimpleDateFormat.(SimpleDateFormat.java:258)

the format im trying to achieve is "2017-06-16T12:19:59.001+02:00"

according to the documentation this pattern should work Whats wrong?

EDIT To clarify, i tried with xxx and XXX

in case of XXX i get java.lang.IllegalArgumentException: Unknown pattern character 'X'

Answer 1

See Update below.

Unfortunately, regarding uppercase X, the documentation [was at the time of the question and this answer] wrong. Since the documentation seems to have changed significantly regarding x and X, I'll go ahead and state here that right now, it says X (uppercase) is supported (since API level 1), but x (lowercase) is not mentioned at all. The docs used to not mention X either.

A check of the Android source code (see validateFormat()) shows that only the letters GyMdkHmsSEDFwWahKzZLc are recognized in that version, despite the docs' claim that X has been supported since API level 1. This explains why you're getting the IllegalArgumentException: Unknown pattern character 'X'.

See this bug report for historical details.

Meanwhile, you'll have to find a workaround, which will vary depending on what kind of input you need to parse. E.g. the OP's answer.

Update: X is available only from Nougat+.

The documentation has now been fixed to add a "Supported (API Levels)" column, which indicates that X is only supported starting from API level 24. Presumably the OP's IllegalArgumentException was due to testing the app on a pre-24 device, since the docs didn't say anything about supported API levels before.