Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]

Groups > comp.lang.java.programmer > #33417

Re: How to write constructor for an abstarct class?

Show all headers | View raw

No, putting trolling aside.
There are a couple of reasons for abstract classes.

1) There is a certain design school which says base
    classes should be always abstract, only non-base
    classes should not be abstract.

    Example from Swing (didn't check): Shape, it
      has subclasses like Ellipse2D, Rectangle2D etc..

    The design rule is often broken, like we might
    have Point2D, and then suddently a NamedPoint2D,
    without a common abstract super class.

2) Prior to default methods in interfaces, an abstract
    class could be used in place of an interface,
    provided extending this abstract class is all that
    is needed.

    Example from Swing (didn't check): AbstractButton
       Could also go with an interface that specifies
       what a button is, could then create hermaphrodites
       like a table which is also a button (well, probably
       doesn't make sense, but anyway)

    The error message of the compiler is both an advantage
    and drawback. The advantage is that the developer is
    reminded what methods need to be implemented.

    The disadvantage is that the design is rendered fragile.
    If I decide to add one more abstract method, all sub-
    classes don't compile anymore.

3) Spaghetti Monster, is it abstract or concrete?
    if it is abstract, no instances would exist, but we
    can see it. Its a knawel of spaghetti with two meat
    balls. So I guess its not abstract.

Bye

j4n bur53 schrieb:
> Eric Douglas schrieb:
>> The real question is why would you want an abstract Shape?
>
> The real question do we see the spaghetti monster in the shape.

Back to comp.lang.java.programmer | Previous | Next — Previous in thread | Next in thread | Find similar | Unroll thread

Thread

How to write constructor for an abstarct class? Xue Feng <xf.lotus@yahoo.com> - 2015-12-28 20:44 +0800
  Re: How to write constructor for an abstarct class? Eric Sosman <esosman@comcast-dot-net.invalid> - 2015-12-28 08:21 -0500
    Re: How to write constructor for an abstarct class? Jan Burse <janburse@fastmail.fm> - 2015-12-28 19:20 +0100
      Re: How to write constructor for an abstarct class? Jan Burse <janburse@fastmail.fm> - 2015-12-28 19:25 +0100
        Re: How to write constructor for an abstarct class? Jan Burse <janburse@fastmail.fm> - 2015-12-28 19:28 +0100
          Re: How to write constructor for an abstarct class? Lew <lewbloch@gmail.com> - 2015-12-28 10:40 -0800
          Re: How to write constructor for an abstarct class? Eric Douglas <e.d.programmer@gmail.com> - 2015-12-28 10:42 -0800
            Re: How to write constructor for an abstarct class? Eric Sosman <esosman@comcast-dot-net.invalid> - 2015-12-28 14:29 -0500
            Re: How to write constructor for an abstarct class? j4n bur53 <janburse@fastmail.fm> - 2015-12-28 22:26 +0100
              Re: How to write constructor for an abstarct class? Eric Douglas <e.d.programmer@gmail.com> - 2015-12-28 13:37 -0800
              Re: How to write constructor for an abstarct class? j4n bur53 <janburse@fastmail.fm> - 2015-12-28 22:47 +0100
                Re: How to write constructor for an abstarct class? Eric Douglas <e.d.programmer@gmail.com> - 2015-12-28 13:58 -0800
                Re: How to write constructor for an abstarct class? j4n bur53 <janburse@fastmail.fm> - 2015-12-28 23:06 +0100
                Re: How to write constructor for an abstarct class? Eric Sosman <esosman@comcast-dot-net.invalid> - 2015-12-28 17:43 -0500
                Re: How to write constructor for an abstarct class? Lew <lewbloch@gmail.com> - 2015-12-28 15:14 -0800
                Re: How to write constructor for an abstarct class? j4n bur53 <janburse@fastmail.fm> - 2015-12-29 15:02 +0100
                Re: How to write constructor for an abstarct class? Arne Vajhøj <arne@vajhoej.dk> - 2015-12-29 15:37 -0500
                Re: How to write constructor for an abstarct class? Arne Vajhøj <arne@vajhoej.dk> - 2015-12-29 15:28 -0500
            Re: How to write constructor for an abstarct class? Arne Vajhøj <arne@vajhoej.dk> - 2015-12-29 15:21 -0500
              Re: How to write constructor for an abstarct class? Arne Vajhøj <arne@vajhoej.dk> - 2015-12-29 15:22 -0500
  Re: How to write constructor for an abstarct class? j4n bur53 <janburse@fastmail.fm> - 2015-12-29 16:24 +0100

csiph-web