Java Tip #9 - unboxing and the elusive npe

Be aware that unboxing can cause a NullPointerException.
Suppose I have this function.

public void test(int a) {
  ...
}

and I declare this variable

  Integer x = null;

then when I make this call

  test(x)

I get a NullPointerException as x is "unboxed" to an int. A more specific exception such as "NullPointerExceptionDueToUnboxingYouMoron" would have helped.

Enjoy.