EVALUATION
The current specification of Boolean is as precise as the JLS currently allows and the caching of the valueOf method is already required.
Closing as will not fix.
10-09-2009
EVALUATION
While the JLS does require that the same object be return wheneven, say, a "true" value is boxed, strictly speaking it does not currently require Boolean.TRUE to be returned:
5.1.7 Boxing Conversion
http://java.sun.com/docs/books/jls/third_edition/html/conversions.html#5.1.7
However, it may be worthwhile to at least state this implementation point.