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

Groups > comp.lang.java.programmer > #38540

Re: Is there a better way to group and sort objects?

Show all headers | View raw

On Wednesday, August 8, 2018 at 10:32:06 AM UTC-4, Eric Sosman wrote:
> >> [...]
> >>       (2) Concerning "unique object pointers," have you learned about the
> >> equals() and hashCode() methods yet?  ;)
> >>
> > I tried writing an equals method but didn't seem useful if I have to call it manually, was hoping it could be used for such purpose as making the objects themselves the key to a map.  Is hashCode() supposed to be used for this purpose?  I thought that was always supposed to have a generated value unique for every object instance.
> 
>      Are you trolling?  You've been participating in this forum for
> upwards of three years, and last year you said you'd been writing
> Java "for probably about 10 years" -- and we're supposed to believe you
> don't know what equals() and hashCode() are for?
> 
>      Benefit of the doubt: I guess it's just barely possible that after
> eleven-ish (claimed) or three-plus (shown) years of Java involvement
> you might actually be unfamiliar with the basics.  You have shown more
> than once that your grasp of Java concepts is less than firm, and I have
> speculated that you may be trying to write Java by "faking it" with an
> extensive knowledge of other languages.  (I still consider that the most
> likely explanation for your blunders, although the Troll Hypothesis is
> beginning to gain credibility.)  But just in case you're not trolling,
> 
> 	F E R   P E T E ' S   S A K E ,   R E A D   A   B O O K !
> 

I have neither time nor money to take a class in Java.  I graduated college in 1996, Java wasn't a thing yet.  I have coded in several languages, starting with COBOL, now primarily in a Business BASIC language which is now a hybrid Java integrated with a custom interpreter which can create Java objects using not quite Java syntax.  We started an in house Java API somewhere around 2008.

I taught myself most everything I know from the Oracle documentation.  The documentation on Object seems a bit vague, as it says hashCode() is typically an integer representation of the internal address of the object, and if equals returns true then the hashCode of the 2 instances must match but if equals returns false they don't have to match.  I didn't see in there exactly where or how equals or hashCode are used, so 1) I wasn't sure which of these methods might be called by the Oracle methods (Map.put?) and 2) if it's a good idea to customize the hashCode.  Should hashCodes be unique to each object instance, or should they return the same value if as in this example a ship to address object and a bill to address object refer to the same physical address?

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

Thread

Is there a better way to group and sort objects? Eric Douglas <e.d.programmer@gmail.com> - 2018-08-07 06:00 -0700
  Re: Is there a better way to group and sort objects? Eric Sosman <esosman@comcast-dot-net.invalid> - 2018-08-07 09:44 -0400
    Re: Is there a better way to group and sort objects? Eric Sosman <esosman@comcast-dot-net.invalid> - 2018-08-07 11:33 -0400
    Re: Is there a better way to group and sort objects? Eric Douglas <e.d.programmer@gmail.com> - 2018-08-07 10:22 -0700
      Re: Is there a better way to group and sort objects? Eric Sosman <esosman@comcast-dot-net.invalid> - 2018-08-07 14:16 -0400
        Re: Is there a better way to group and sort objects? Eric Sosman <esosman@comcast-dot-net.invalid> - 2018-08-07 14:36 -0400
        Re: Is there a better way to group and sort objects? Eric Douglas <e.d.programmer@gmail.com> - 2018-08-07 12:13 -0700
          Re: Is there a better way to group and sort objects? Eric Sosman <esosman@comcast-dot-net.invalid> - 2018-08-07 16:00 -0400
  Re: Is there a better way to group and sort objects? Martin Gregorie <martin@mydomain.invalid> - 2018-08-08 08:20 +0000
    Re: Is there a better way to group and sort objects? Eric Sosman <esosman@comcast-dot-net.invalid> - 2018-08-08 06:57 -0400
      Re: Is there a better way to group and sort objects? Martin Gregorie <martin@mydomain.invalid> - 2018-08-08 11:08 +0000
      Re: Is there a better way to group and sort objects? Martin Gregorie <martin@mydomain.invalid> - 2018-08-08 11:22 +0000
        Re: Is there a better way to group and sort objects? Eric Sosman <esosman@comcast-dot-net.invalid> - 2018-08-08 07:45 -0400
          Re: Is there a better way to group and sort objects? Martin Gregorie <martin@mydomain.invalid> - 2018-08-08 14:12 +0000
        Re: Is there a better way to group and sort objects? Eric Douglas <e.d.programmer@gmail.com> - 2018-08-08 05:50 -0700
          Re: Is there a better way to group and sort objects? Eric Sosman <esosman@comcast-dot-net.invalid> - 2018-08-08 09:23 -0400
            Re: Is there a better way to group and sort objects? Eric Douglas <e.d.programmer@gmail.com> - 2018-08-08 06:47 -0700
              Re: Is there a better way to group and sort objects? Eric Sosman <esosman@comcast-dot-net.invalid> - 2018-08-08 10:31 -0400
                Re: Is there a better way to group and sort objects? Eric Douglas <e.d.programmer@gmail.com> - 2018-08-08 08:24 -0700
          Re: Is there a better way to group and sort objects? Robert Klemme <shortcutter@googlemail.com> - 2018-08-14 14:06 +0200
            Re: Is there a better way to group and sort objects? Eric Douglas <e.d.programmer@gmail.com> - 2018-08-14 05:49 -0700
  Re: Is there a better way to group and sort objects? Daniele Futtorovic <da.futt.news@laposte-dot-net.invalid> - 2018-08-09 16:06 +0200
    Re: Is there a better way to group and sort objects? Eric Douglas <e.d.programmer@gmail.com> - 2018-08-14 05:47 -0700

csiph-web