From the Javadoc for Character#getNumericValue
:
If the character does not have a numeric value, then -1 is returned. If the character has a numeric value that cannot be represented as a nonnegative integer (for example, a fractional value), then -2 is returned.
The character +
does not have a numeric value, so you're getting -1.
Update:
The reason that primitive conversion is giving you 43 is that the the character '+' is encoded as the integer 43.