Re: Signature mismatch when calling java prototype

Just a couple of comments regarding Java basics. Dan probably covered
them below, but:

1. By convention, the Java runtime finds the starting point of an
application by invoking a main() method with this signature:

public static void main( String[] args )

If such a method doesn't exist, a standard runtime ( invoking java
MyOwnClass or the RUNJAVA equivalent ) won't start the app and returns a
NoSuchMethodError.

You can have multiple methods ( with different signatures, like any
other method ) *OR* no methods named main. The reasons normally cited are
method overloading/overriding, or that an object may be intended to only be
instantiated by methods from other classes, so it doesn't need a main()
method.

2. A static method doesn't need an instance; it's available at class
load time. But, although it's frowned upon, you *can* still call a static
( that is, a class ) method via an instance. i.e.

MyOwnClass moc = new MyOwnClass();

moc.myStaticMethod();

That's likely due to inheritance, but in implementations the compiler
probably just realizes a static method is being requested and substitutes
the appropriate call.

HTH,


Joe Sam

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----- Original Message ----- From: "Dan Kimmel" <dkimmel@xxxxxxxxxxxxxxx>
To: "Java Programming on and around the IBM i" <java400-l@xxxxxxxxxxxx>
Sent: Tuesday, March 08, 2011 1:44 PM
Subject: RE: Signature mismatch when calling java prototype

Like Barbara said, STATIC.

There's nothing wrong with using STATIC procedures (now that I know the
syntax :-) ). You don't have to go through the pain of running the
CONSTRUCTOR first. If you don't need instance objects, don't use them.
Referencing a static method automatically creates the class object the
first time you use it, but no instance objects. The class object contains
only the static members and methods. But don't call it "main". A class
does not have to have a "main" unless you want the RUNJVA command to start
there. Java function main is really meant for just that; the place to
start when the JVM starts up. You can specify any other function as
static. In fact, you can have a static method and non-static method with
the same name; they'll have different signatures.

So here's what I'd suggest for your prototype:

ResendOrder pr o STATIC extproc(*JAVA:
'com.WMS_BPCS_Integrator.ex-
ecutable.ResendOrder':'resendOrder')
class(*JAVA:'java.lang.String')
o class(*JAVA:'java.lang.String')
dim(2)

And your method definition should look like this:

String static resendOrder(String[] input{
return "gotcha";
}

I just noticed you're passing in a String array (dim(2)) and not two
String's. Of course that's the classic signature for the JVM startup
method: static void main(String[] xx)