Why do Double.parseDouble(null) and Integer.parseI

问题:

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

Is this a historical accident or intentional? The documentation clearly states two types of exceptions for Double.parseDouble(...) and one for Integer.parseInt(), but it seems inconsistent:

Integer.parseInt(null); // throws java.lang.NumberFormatException: null

However

Double.parseDouble(null); // throws java.lang.NullPointerException

回答1:

It is reasonable to expect the same exceptions to be thrown for null; however, these api's are very old and may not be able to be changed at this point.

And:

Since the exception behavior is long-standing and specified in the JavaDoc, it is impractical to change either method's behavior at this time. Closing as will not fix.

As taken from: Bug Report: Integer.parseInt() and Double.parseDouble() throw different exceptions on null.

Like others have stated: It's likely made by different authors.

回答2:

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.