[1841] in java-interest
Re: questions
daemon@ATHENA.MIT.EDU (Arthur van Hoff)
Mon Sep 18 19:33:17 1995
Date: Mon, 18 Sep 1995 11:49:34 -0800 (PDT)
From: Arthur van Hoff <Arthur.Vanhoff@Eng.Sun.COM>
Reply-To: Arthur van Hoff <Arthur.Vanhoff@Eng.Sun.COM>
To: Frank Greco <fgreco@lehman.com>
Cc: java-interest@java.Eng.Sun.COM
Hi Frank,
> 1. What is the equivalent in J/HJ of writing CGI-scripts? How does
> one grab input from a local "form" and pass it to a remote machine
> for processing?
You can write an applet that does the equivalent of a form (and a lot more).
We will probably be providing better hookups to existing forms in the future.
> 2. The docs (McGilton/Gosling) mention remote invocation of methods.
> How does one do this in Java? I didn't see any reference to
> this in any other documentation. I'd like for one Java object
> to invoke a method in another; and both objects are distributed
> (ie, non-local).
The DOE project is working on a CORBA style solution for this.
> 3. To perform the functional equivalent of multiple inheritance, the
> docs say to use "interfaces" (talk about overloading...). But it
> seems to me that interfaces are merely a way to collect or organize
> functions in a class-ish way. A bottom line question: How does
> one inherit a method from one object *and* a method from another object
> where both objects are from a third-party package?
You can only do implementation inheritance by delegation.
> 4. What is exactly meant by "package of a file" or "to package"? The
> docs are quite ambiguous. Does it merely mean to include a class
> into a module, similar to archiving?
I'm not sure I understand the question. Packages are collections of classes.
Each class is a file and a package is a directory full of classes.
> 5. If, during the course of running an application/applet, a Java pgm
> needs to instantiate superclasses, where "path" does it use to get
> the superclasses? Can I instruct the app to get it from another
> URL in the web?
Not currently but the class loader (which is part of the browser) can
allow you to do that. It decides where to load classes from. Our current
policy loads classes from a single source URL.
> 6. Does Java have a mechanism of versioning classes? That is, how can
> a user of a Java app[let] continue to use an older version of a
> particular class when I (as app author) upgrade my app[let].
> Excuse the gross analogy, but is there an equivalent of
> LD_LIBRARY_PATH for Java classes?
We currently don't have a good mechanism for versioning classes. You can
achieve a reasonable versioning scheme using naming conventions, but that is
far from ideal.
> 7. How does one pass-by-value in Java to maintain good software
> engineering style?
I'm not sure I understand. Do you mean pass an array/object by value? We don't
support that.
Have fun,
Arthur van Hoff
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