IStringConverter must NOT be Inner Class

[phreed]

This could be corrected with a change to the documentation.

The problem is that the parameter types for an inner class includes the parent class. https://github.com/cbeust/jcommander/blob/master/src/main/java/com/beust/jcommander/JCommander.java#L1355 This means that the 'ctor' is not set and null is returned for inner class Converters.

[hongwingl]

It can be an inner class, you just have to declare it as static class