Java Puzzle #1

Inspired by Java Puzzlers conference, spotted interesting behaviour of following code:

public class LongNull {
    Long longi = null;

    public long getLongi() {
        return longi;
    }

    public static void main(String[] args) {
        System.out.println(new LongNull().getLongi());
    }
}

What it produces:

1. NullPointerException
2. Prints 0
3. Prints null

Answer is 1. NullPointerException during auto unboxing. Change getLongi() to return Long instead of long fixes this and output will be 'null'.