Path: csiph.com!eternal-september.org!feeder.eternal-september.org!news.eternal-september.org!.POSTED!not-for-mail
From: Cecil Westerhof <Cecil@decebal.nl>
Newsgroups: comp.lang.java.programmer
Subject: Re: Using main from abstract class in concrete class
Date: Sun, 13 Aug 2017 15:43:15 +0200
Organization: Decebal Computing
Lines: 84
Message-ID: <871sofwpl8.fsf@munus.decebal.nl>
References: <87h8xbx0ig.fsf@munus.decebal.nl> <new-Main-20170813112247@ram.dialup.fu-berlin.de>
Mime-Version: 1.0
Content-Type: text/plain; charset=utf-8
Content-Transfer-Encoding: 8bit
Injection-Info: mx02.eternal-september.org; posting-host="1615173a1409002a85fbdd25ac4b9ead"; logging-data="31362"; mail-complaints-to="abuse@eternal-september.org";	posting-account="U2FsdGVkX1/FKmCqYY6cHiNN0VDMV3StKH1eRCUr4wE="
User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/24.5 (gnu/linux)
Cancel-Lock: sha1:wQ5IXNaBufDNbqxDcAgdU+MZp2E= sha1:oN3mZ9fVsCo0dZ1dYef67f8KMsg=
X-Homepage: http://www.decebal.nl/
Xref: csiph.com comp.lang.java.programmer:37178

ram@zedat.fu-berlin.de (Stefan Ram) writes:

> Cecil Westerhof <Cecil@decebal.nl> writes:
>>I have an abstract class. There can be several concrete classes that
>>extend this class. Is it possible to write a main in the abstract
>>class which will be used by the concrete classes and that in the main
>>a instance of the concrete class is created?
>
>   The noun phrase »a main« does not have a general meaning in the
>   Java community. I assume you mean a method with the well-known
>   proclamation
>
> public static void main( final java.lang.String[] args )

Yes, that was what I mend. I should have been more clear.


>
>   . Main.java
>
> abstract class Abstract
> { 
>   public static void main( final java.lang.String[] args ) 
>   { try
>     { java.lang.Class.forName( args[ 0 ]).
>       getDeclaredConstructor().newInstance(); } 
>     catch
>     ( final 
>       java.lang.ClassNotFoundException | 
>       java.lang.NoSuchMethodException | 
>       java.lang.InstantiationException | 
>       java.lang.IllegalAccessException | 
>       java.lang.reflect.InvocationTargetException
>       exception )
>     { java.lang.System.err.println( exception ); }}}
>
> public final class Main extends Abstract
> { 
>
>   public Main()
>   { java.lang.System.out.println( "new Main()" ); }
>
>   public static void main( final java.lang.String[] args ) 
>   { final java.lang.String[] arguments =
>     { Main.class.getCanonicalName() };
>     Abstract.main( arguments ); }}
>
>   transcript
>
> new Main()
>

At the moment I have:
    public static void main(final String[] args) throws SQLException {
        SQL.mainWork(SQLite3.class.getCanonicalName(), args);
    }

And in SQL.java I have:
    static void mainWork(final String className, final String[] args)
        throws SQLException {
        String   action;
        String   database;
        String[] parameters;

        if (args.length < 2) {
            System.err.println("Need at least two parameters: command and database.");
            System.exit(1);
        }
        // First  argument is action
        // Second argument is database
        action     = args[0];
        database   = args[1];
        parameters = Arrays.copyOfRange(args, 2, args.length);
        try {
            SQL connection = (SQL) Class.forName(className)
                .getDeclaredConstructor(new Class<?>[] {String.class})
                .newInstance(database);
            switch (action) {
            case "--testConnection":

-- 
Cecil Westerhof
Senior Software Engineer
LinkedIn: http://www.linkedin.com/in/cecilwesterhof