Groups > comp.lang.java.programmer > #10536

Re: Collection to implement linked structure traverse up and down

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From	Lew <lewbloch@gmail.com>
Newsgroups	comp.lang.java.programmer
Subject	Re: Collection to implement linked structure traverse up and down
Date	Mon, 5 Dec 2011 15:08:29 -0800 (PST)
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ruds wrote:
> Roedy Green: Can you elaborate some more on "a HashMap an ArrayList
> and a TreeSet simultaneously all on the same group of objects."

Consider this fragment:

 Map<Foo, Bar> bars = new HashMap<>();
 List<Bar> barVals = new ArrayList<>();
 Set<Foo> foos = new TreeSet<>();
...
 Foo foo = new Foo();
 Bar bar = new Bar();
 bars.put(foo, bar);
 barVals.add(bar);
 foos.add(foo);
...

A pointer to the same 'foo' appears in 'bars' and in 'foos'.  A pointer to the same 'bar' appears in 'bars' and in 'barVals'.

Do that again with a new 'foo' and a new 'bar' a few times and you have "a group of objects" in all three collections simultaneously.

-- 
Lew

Thread

Collection to implement linked structure traverse up and down ruds <rudranee@gmail.com> - 2011-11-27 23:53 -0800
  Re: Collection to implement linked structure traverse up and down Arved Sandstrom <asandstrom3minus1@eastlink.ca> - 2011-11-28 07:32 -0400
    Re: Collection to implement linked structure traverse up and down Wayne <nospam@all.invalid> - 2011-12-01 10:39 -0500
      Re: Collection to implement linked structure traverse up and down ruds <rudranee@gmail.com> - 2011-12-04 23:57 -0800
        Re: Collection to implement linked structure traverse up and down Lew <lewbloch@gmail.com> - 2011-12-05 15:08 -0800
          Re: Collection to implement linked structure traverse up and down ruds <rudranee@gmail.com> - 2011-12-05 21:55 -0800
  Re: Collection to implement linked structure traverse up and down Roedy Green <see_website@mindprod.com.invalid> - 2011-11-29 17:01 -0800
    Re: Collection to implement linked structure traverse up and down Henk van Voorthuijsen <voorth@xs4all.nl> - 2011-12-05 02:41 -0800
  Re: Collection to implement linked structure traverse up and down Martin Gregorie <martin@address-in-sig.invalid> - 2011-11-30 21:17 +0000

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