A DESCRIPTION OF THE REQUEST :
When java attempts to unbox a null value, it produces a NullPointerException, which is correct, but not as useful as it could be. It would be far more useful to return a new exception titled something like UnboxingNullValueException or UnboxingException.

JUSTIFICATION :
1) Prior to the introduction of boxing/unboxing, the only way to get an NPE was to use the dot operator, as in s.toString().length(). Now it is possible to get one through an implicit operation. Since these are fairly rare exceptions, most developers would first look at every use of the dot operator to see which one was call from a null object. Only after that fails would we then consider other possibilities

2) Unboxing is an implicit operation, so if we look at the code, trying to find out what's wrong with it, we're not likely to spot it, because that's not where the problem lies.

3) Everywhere else we see a NullPointerException, we look at the places where we used the dot operator. If this exception requires a different debugging strategy, it should have a different name.

This is especially confusing for beginners, although an experienced developer like myself gets caught by this.

In the submitted code, three lines are marked with "// np". These are lines that may throw a NullPointerException due to unboxing.

At np 1, the dot operator isn't used. (This is not very common)
At np 2, it appears that bug is the null value.
At np 3, the most common case, the dot operator is used more than once, so I start checking the values of variables that have nothing to do with the problem. (The last time I saw this problem, the line of code used the dot 49 times. I was chaining my calls, as in StringBuffer.append(). A more descriptive error message would have been far more helpful.)

If all of these instead threw an UnboxingNullValueException (which could extend NullPointerException), it would point me straight to the problem instead of leading me astray.

EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
When attempting to unbox a value that is equal to null, I would like to see an exception thrown that is unique to the unboxing operation, and that says so in its name.
ACTUAL -
I get a "NullPointerException," which, while it's correct, isn't very useful and is surprisingly misleading.



---------- BEGIN SOURCE ----------
public class UnBoxingBug {
private Short size = null;

public static void main(String[] args) {
execute();
}

private Short getSize() { return size; }

private int getArea() {
return getSize()*getSize(); // np 1
}

private static void execute() {
UnBoxingBug bug = new UnBoxingBug();
int x = bug.getSize(); // np 2
int y = bug.getArea();
int z = bug.toString().length() * bug.getSize(); // np 3
}
}
---------- END SOURCE ----------