Re: Command-line arg

On Oct 19, 4:34 pm, Wayne <nos...@xxxxxxxxxxxxxx> wrote:
Mark Space wrote:
It is theoretically possible for main() to be called with a null
argument. You may wish to check for this also or risk throwing a
NullPointer exception.

Nope. Section 12.1.4 of the JLS:
<quote>
The method main must be declared public, static, and void. It must
accept a single argument that is an array of strings. This method
can be declared as either

public static void main(String[] args)

or

public static void main(String... args)
</quote>

And Section 2.16.1 of the JVM spec:
<quote>
A Java Virtual Machine starts execution by invoking the
method main of some specified class, passing it a single
argument, which is an array of Strings. ...
</quote>

I think the only legal but not stated variation is declaring
main as:
public static void main ( String args[] )

So, if your JVM is capable of passing a null to main,
it is not a legal JVM. Invoking args.length in main
can not throw a NullPointerException in any valid JRE.

Have you ever run across a JVM that passed a NULL to main?
I've never tested any JVMs for that, but if there are
popular JVMs that do this I guess such a test would be
worthwhile.

-Wayne

Who said it was the JVM who passed it in?
SomeClass.main(new String[] {null, "oops", "npe"});
SomeClass.main(null);


.

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