Groups > comp.lang.java.programmer > #36865

Re: How to assign an object to another in it method?

From	Andreas Leitgeb <avl@logic.at>
Newsgroups	comp.lang.java.programmer
Subject	Re: How to assign an object to another in it method?
Date	2017-07-12 16:23 +0000
Organization	A noiseless patient Spider
Message-ID	<slrnomcjfv.o2q.avl@logic.at> (permalink)
References	(16 earlier) <ojs35k$hf4$1@jstuckle.eternal-september.org> <slrnoma4gp.o2q.avl@logic.at> <ok39b0$eic$1@jstuckle.eternal-september.org> <ok3qco$jk0$2@gioia.aioe.org> <ok3ujr$d31$1@jstuckle.eternal-september.org>

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Jerry Stuckle <jstucklex@attglobal.net> wrote:
> Nope.  In the strictest sense is is NOT a valid derived class.  The
> rules given for Employee were that wage must be >= minimum wage.  The
> rules for Manager do not include that restriction.  Therefore it is an
> invalid inheritance - no matter what you name them.

Welcome to the topic of covariant versus contravariant types.

If I have a square (e.g. a unit square), then this square *is*
also *a* rectangle.

If I have a class Rectangle and a class Square, then Square
is a subclass of Rectangle (as every square is obviously also 
a rectangle). But then  Rectange  may have a method to *set*
both side lengths. But Square would not allow to set two
different lengths.

Question: is a Square a Rectangle, or is a Rectange a Square?
Answer: depends...

PS: that's also why Java generics offer <T super S> for certain uses.

Thread

How to assign an object to another in it method? parmenides <xparmenides@yahoo.com> - 2017-06-18 20:02 +0800
  Re: How to assign an object to another in it method? Eric Sosman <esosman@comcast-dot-net.invalid> - 2017-06-18 08:09 -0400
  Re: How to assign an object to another in it method? Robert Klemme <shortcutter@googlemail.com> - 2017-06-18 15:31 +0200
  Re: How to assign an object to another in it method? Eric Sosman <esosman@comcast-dot-net.invalid> - 2017-06-19 10:22 -0400
    Re: How to assign an object to another in it method? Eric Douglas <e.d.programmer@gmail.com> - 2017-06-19 08:13 -0700
      Re: How to assign an object to another in it method? Eric Sosman <esosman@comcast-dot-net.invalid> - 2017-06-19 11:53 -0400
        Re: How to assign an object to another in it method? Eric Douglas <e.d.programmer@gmail.com> - 2017-06-19 09:06 -0700
          Re: How to assign an object to another in it method? Eric Sosman <esosman@comcast-dot-net.invalid> - 2017-06-19 13:56 -0400
      Re: How to assign an object to another in it method? lewbloch@gmail.com - 2017-06-27 13:49 -0700
        Re: How to assign an object to another in it method? Andreas Leitgeb <avl@logic.at> - 2017-06-28 12:20 +0000
          Re: How to assign an object to another in it method? Eric Douglas <e.d.programmer@gmail.com> - 2017-06-28 05:51 -0700
            Re: How to assign an object to another in it method? Eric Sosman <esosman@comcast-dot-net.invalid> - 2017-06-28 14:03 -0400
            Re: How to assign an object to another in it method? Arne Vajhøj <arne@vajhoej.dk> - 2017-07-02 21:23 -0400
              Re: How to assign an object to another in it method? Martin Gregorie <martin@address-in-sig.invalid> - 2017-07-03 10:59 +0000
                Re: How to assign an object to another in it method? Arne Vajhøj <arne@vajhoej.dk> - 2017-07-03 08:38 -0400
                Re: How to assign an object to another in it method? Andreas Leitgeb <avl@logic.at> - 2017-07-03 14:04 +0000
                Re: How to assign an object to another in it method? Jerry Stuckle <jstucklex@attglobal.net> - 2017-07-03 10:39 -0400
                Re: How to assign an object to another in it method? Andreas Leitgeb <avl@logic.at> - 2017-07-03 16:28 +0000
                Re: How to assign an object to another in it method? Jerry Stuckle <jstucklex@attglobal.net> - 2017-07-03 16:52 -0400
                Re: How to assign an object to another in it method? Arne Vajhøj <arne@vajhoej.dk> - 2017-07-03 22:04 -0400
                Re: How to assign an object to another in it method? Jerry Stuckle <jstucklex@attglobal.net> - 2017-07-03 23:15 -0400
                Re: How to assign an object to another in it method? Arne Vajhøj <arne@vajhoej.dk> - 2017-07-04 21:46 -0400
                Re: How to assign an object to another in it method? Jerry Stuckle <jstucklex@attglobal.net> - 2017-07-04 22:18 -0400
                Re: How to assign an object to another in it method? Arne Vajhøj <arne@vajhoej.dk> - 2017-07-08 21:13 -0400
                Re: How to assign an object to another in it method? Jerry Stuckle <jstucklex@attglobal.net> - 2017-07-08 22:12 -0400
                Re: How to assign an object to another in it method? Andreas Leitgeb <avl@logic.at> - 2017-07-11 17:56 +0000
                Re: How to assign an object to another in it method? Jerry Stuckle <jstucklex@attglobal.net> - 2017-07-11 15:40 -0400
                Re: How to assign an object to another in it method? Eric Douglas <e.d.programmer@gmail.com> - 2017-07-11 13:49 -0700
                Re: How to assign an object to another in it method? Jerry Stuckle <jstucklex@attglobal.net> - 2017-07-11 17:41 -0400
                Re: How to assign an object to another in it method? Arne Vajhøj <arne@vajhoej.dk> - 2017-07-11 20:27 -0400
                Re: How to assign an object to another in it method? Jerry Stuckle <jstucklex@attglobal.net> - 2017-07-11 21:43 -0400
                Re: How to assign an object to another in it method? Arne Vajhøj <arne@vajhoej.dk> - 2017-07-11 21:49 -0400
                Re: How to assign an object to another in it method? Jerry Stuckle <jstucklex@attglobal.net> - 2017-07-12 17:20 -0400
                Re: How to assign an object to another in it method? Andreas Leitgeb <avl@logic.at> - 2017-07-13 10:08 +0000
                Re: How to assign an object to another in it method? Martin Gregorie <martin@address-in-sig.invalid> - 2017-07-13 11:35 +0000
                Re: How to assign an object to another in it method? Arne Vajhøj <arne@vajhoej.dk> - 2017-07-13 08:14 -0400
                Re: How to assign an object to another in it method? Martin Gregorie <martin@address-in-sig.invalid> - 2017-07-13 14:29 +0000
                Re: How to assign an object to another in it method? Arne Vajhøj <arne@vajhoej.dk> - 2017-07-13 13:47 -0400
                Re: How to assign an object to another in it method? Andreas Leitgeb <avl@logic.at> - 2017-07-13 18:09 +0000
                Re: How to assign an object to another in it method? Arne Vajhøj <arne@vajhoej.dk> - 2017-07-13 15:01 -0400
                Re: How to assign an object to another in it method? Andreas Leitgeb <avl@logic.at> - 2017-07-13 19:19 +0000
                Re: How to assign an object to another in it method? Arne Vajhøj <arne@vajhoej.dk> - 2017-07-13 15:39 -0400
                Re: How to assign an object to another in it method? Andreas Leitgeb <avl@logic.at> - 2017-07-13 16:49 +0000
                Re: How to assign an object to another in it method? Jerry Stuckle <jstucklex@attglobal.net> - 2017-07-13 10:24 -0400
                Re: How to assign an object to another in it method? Andreas Leitgeb <avl@logic.at> - 2017-07-13 17:19 +0000
                Re: How to assign an object to another in it method? Arne Vajhøj <arne@vajhoej.dk> - 2017-07-13 21:17 -0400
                Re: How to assign an object to another in it method? Andreas Leitgeb <avl@logic.at> - 2017-07-14 06:40 +0000
                Re: How to assign an object to another in it method? Arne Vajhøj <arne@vajhoej.dk> - 2017-07-14 14:26 -0400
                Re: How to assign an object to another in it method? Andreas Leitgeb <avl@logic.at> - 2017-07-15 14:36 +0000
                Re: How to assign an object to another in it method? Jerry Stuckle <jstucklex@attglobal.net> - 2017-07-14 12:10 -0400
                Re: How to assign an object to another in it method? Arne Vajhøj <arne@vajhoej.dk> - 2017-07-14 14:40 -0400
                Re: How to assign an object to another in it method? Jerry Stuckle <jstucklex@attglobal.net> - 2017-07-14 14:51 -0400
                Re: How to assign an object to another in it method? Arne Vajhøj <arne@vajhoej.dk> - 2017-07-14 21:05 -0400
                Re: How to assign an object to another in it method? Arne Vajhøj <arne@vajhoej.dk> - 2017-07-14 21:06 -0400
                Re: How to assign an object to another in it method? lewbloch@gmail.com - 2017-07-14 14:44 -0700
                Re: How to assign an object to another in it method? Andreas Leitgeb <avl@logic.at> - 2017-07-12 16:23 +0000
                Re: How to assign an object to another in it method? Eric Douglas <e.d.programmer@gmail.com> - 2017-07-12 10:12 -0700
                Re: How to assign an object to another in it method? Arne Vajhøj <arne@vajhoej.dk> - 2017-07-11 20:16 -0400
                Re: How to assign an object to another in it method? Jerry Stuckle <jstucklex@attglobal.net> - 2017-07-11 21:46 -0400
                Re: How to assign an object to another in it method? Arne Vajhøj <arne@vajhoej.dk> - 2017-07-11 21:52 -0400
                Re: How to assign an object to another in it method? Arne Vajhøj <arne@vajhoej.dk> - 2017-07-11 20:24 -0400
                Re: How to assign an object to another in it method? Jerry Stuckle <jstucklex@attglobal.net> - 2017-07-11 21:49 -0400
                Re: How to assign an object to another in it method? Arne Vajhøj <arne@vajhoej.dk> - 2017-07-11 21:55 -0400
                Re: How to assign an object to another in it method? Martin Gregorie <martin@address-in-sig.invalid> - 2017-07-03 12:37 +0000
                Re: How to assign an object to another in it method? Eric Sosman <esosman@comcast-dot-net.invalid> - 2017-07-03 11:34 -0400
                Re: How to assign an object to another in it method? Martin Gregorie <martin@address-in-sig.invalid> - 2017-07-03 17:28 +0000
  Re: How to assign an object to another in it method? v_borchert@despammed.com (Volker Borchert) - 2017-06-19 17:13 +0000
  Re: How to assign an object to another in it method? Eric Douglas <e.d.programmer@gmail.com> - 2017-06-19 13:40 -0700

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