[misc] Address Sonar warnings

* Subsumed exceptions
* Concrete rather than interface type (HashMap vs Map, etc.)
* Boxed value is unboxed and then immediately reboxed
* String To String
* Superfluous String.valueOf(...)

Change-Id: Ibb1ef8f869959a45f09329d3fe579f6006a8fa95
Signed-off-by: Andreas Sewe <andreas.sewe@codetrails.com>
Signed-off-by: Johannes Dorn <johannes.dorn@codetrails.com>