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Re: "Hello world!" without a public class?

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  Re: "Hello world!" without a public class? Lew <lewbloch@gmail.com> - 2013-01-06 00:44 -0800
    Re: "Hello world!" without a public class? Robert Klemme <shortcutter@googlemail.com> - 2013-01-06 11:47 +0100

#21016 — Re: "Hello world!" without a public class?

Stefan Ram wrote:
> »class HelloWorldApp {
>     public static void main(String[] args) {
>         System.out.println("Hello World!"); // Display the string.
>     }
> }
> «
> 
> http://docs.oracle.com/javase/tutorial/getStarted/cupojava/win32.html
> 
>   There is no »public« in front of »class« in Oracles Tutorial!
> 
>   What should I teach in my classes?

Depends on the kinds of students you have, I should think.

There's pedagogical merit in teaching the good habits first and the 
exceptional cases later. So you could begin with only 'public' classes 
overall, let alone for the main one, mentioning briefly at first that 
there is a way to drop the 'public' that you'll explain later.

As for 'final', that's harder. Hardly anyone in the field uses it, 
myself included, because most classes basically aren't inherited so it's 
not really risky to leave it out, and also there's a benefit to making 
classes heritable for test purposes.

I think as a teacher I would use 'final' nearly always for classes, and 
explain to the class (of students) that I'm being picky, but for good 
reason. Also I'd mention that heritable classes support a certain style of 
test code, and teach it once inheritance had been covered.

>     1.) »public class HelloWorldApp« (because this is most common IIRC)

First time you deal with class definition, show all these forms once.

>     2.) »class HelloWorldApp« (because this is in Oracles tutorial)

Mention that this rarely occurs in practice.

>     3.) »final class HelloWorldApp« (because this class is not designed
>         for inheritance and Bloch says that one should not inherit from
>         it in this case and the students can as well get used to this
>         right from the start)

package-private again - same brief mention.

>     4.) »public final class HelloWorldApp« (combination of »1.)« and »3.)«)

Go with this but explain that practice can differ.

Break the 'final' later when there is a pedagogical and good-code reason to.

Just off the top of my head - I haven't put nearly the thought into this that 
you have.

-- 
Lew

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#21019

On 06.01.2013 09:44, Lew wrote:

> There's pedagogical merit in teaching the good habits first and the
> exceptional cases later. So you could begin with only 'public' classes
> overall, let alone for the main one, mentioning briefly at first that
> there is a way to drop the 'public' that you'll explain later.

+1

> As for 'final', that's harder. Hardly anyone in the field uses it,
> myself included, because most classes basically aren't inherited so it's
> not really risky to leave it out, and also there's a benefit to making
> classes heritable for test purposes.

I use it rather frequently on the basis of whether I intend a class for 
inheritance or not.  It's easier to loosen a restriction later than the 
other way round.  Plus, it /might/ help the JVM optimize.  But that's 
really the smallest benefit and the most unimportant reason.

> I think as a teacher I would use 'final' nearly always for classes, and
> explain to the class (of students) that I'm being picky, but for good
> reason. Also I'd mention that heritable classes support a certain style of
> test code, and teach it once inheritance had been covered.

That's a bit contradictory, isn't it?  I mean you say that almost nobody 
uses it (including you, and also for good reasons) yet you would 
recommend making it a habit to a beginner. :-)

Kind regards

	robert

-- 
remember.guy do |as, often| as.you_can - without end
http://blog.rubybestpractices.com/

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