When boxed type ``++java.lang.Boolean++`` is used as an expression it will throw ``++NullPointerException++`` if the value is ``++null++`` as defined in https://docs.oracle.com/javase/specs/jls/se8/html/jls-5.html#jls-5.1.8[Java Language Specification §5.1.8 Unboxing Conversion].
It is safer to avoid such conversion altogether and handle the ``++null++`` value explicitly.