I think it is a defect in BDB JE.
A number of JDK defect reports (JDK-6301579, JDK-8037567 ) was raised about the same problem with class initialization, but, they have been closed as "not an issue".
It seems Java spec does not allow static initializers to reference subclasses.
The TupleBinding is parent of IntegerBinding. In static block of TupleBinding an instance of IntegerBinding is created.