Re: Using "abstract" on a class with no abstract method

From:

"Mike Schilling" <mscottschilling@hotmail.com>

Newsgroups:

comp.lang.java.programmer

Date:

Sun, 16 Aug 2009 13:35:54 -0700

Message-ID:

<h69qjc$jge$1@news.eternal-september.org>

Stefan Ram wrote:

Daniel Pitts <newsgroup.spamfilter@virtualinfinity.net> writes:

how about replacing your command structure with method calls:
clock.adjustClock();
clock.incrementCounter();

I think this idea illustrates the meaning of
?straightforward?.

However, my idea is to have a program that can be changed
at runtime. That is, components can be added or removed
from the program as plug-ins at run-time.

Say, the clock component issues a call to the text console
component. In your notation, this is:

textConsole.println( "clock ready." )

However, the user might not have added any text console
component to his program instance. So this can not work.

Instead, the clock component uses:

container.process( new PrintConsoleCommand( "clock ready." ));

Now, if the container happens to be a text console itself,
it will print the text. Otherwise, the text will be
forewarded in such a manner that it will reach all text
console components, if any is present in the program at
all at this moment, otherwise, the message will eventually
be ignored.

I also do not like to have a single communication manager,
because I want local interaction of components. That is,
each component interacts directly only with its container
and its containees.

Is there a master list of commands, or are they added by optional
components as well?

If the former, you could assign each command a numeric value, and
eliminate instanceof by changing command processing to a switch
statement. Even if the latter, you could assign each compnent a
unique namespace and assign numbers within the component. Command
processing becomes

    if (cmd.getNamespace.eq("http:://clock.org")
    {
        switch(cmd.getCommandNumber())
        {
            case CLOCK_SET:
            ...
        }
    }