Why do Double.parseDouble(null) and Integer.parseInt(null) throw different exceptions?

Question

Why do Double.parseDouble(null) and Integer.parseInt(null) throw different exceptions?

Is this a historical accident or intentional? The documentation clearly states

Answer 1

Note: everything in this post is in the source of Java7-b147

Double.parseDouble() goes into a Sun library (in sun.misc.FloatingDecimal) the first important thing that happens is:

in = in.trim(); // don't fool around with white space.
                // throws NullPointerException if null

Integer.parseInt() is done manually in the Integer class. The first important thing that happens is:

if (s == null) {
    throw new NumberFormatException("null");
}

I would guess there are two different authors.