The Formatter spec unfortunately says that "char" is not an integral type.
This disagrees with the JLS specification (4.2.1).
In dividing the conversions into categories, the Formatter spec
says of the integral conversions:

   1. Integral - may be applied to Java integral types: byte, Byte,
      short, Short, int and Integer, long, Long, and BigInteger

It is strange that a Java language integral type is described by the spec
as not being an integral type, and it is strange that it can't be formatted
as a number.