There is a warning in Effective Java (Second Edition, Item #49) regarding the dangers, including throwing of NullPointerException, related to careless mixing of primitive and reference types.

Java is not a particularly beginner-friendly language and it is rife with rigid rules and structures that can be tough to wrap your head around. Then there’s the NullPointerException.

It was announced approximately 18 months ago that JDK 7 would include a new java.util.Objects class that would "hold commonly-written utility methods." As part of this announcement , Joe Darcy ...