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Groups > comp.lang.java.programmer > #35526

Re: ArrayList vs HashMap

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On 8/31/2016 8:55 AM, Andreas Leitgeb wrote:
> Stefan Ram <ram@zedat.fu-berlin.de> wrote:
>>   A HashSet, on the other hand, has a nicer interface for
>>   programmers, so one should write an »ArraySet implements Set«
>>   wrapper for ArrayLists (unless such a thing should already exist).
>
> Unless I missed something, the interface Set doesn't add any method,
> that isn't already in Collection.
>
> If it weren't for Set's specific semantics of add(o) where o was
> already contained, then ArrayList would "already be a Set".

     There's also the matter of equals() and hashCode() semantics:

	Set<String> s1 = new HashSet<>();
	Set<String> s2 = new TreeSet<>();
	s1.add("Hello");  s1.add("World");
	s2.add("World");  s2.add("Hello");
	assert s1.equals(s2);
	assert s1.hashCode() == s2.hashCode();

	List<String> l1 = new ArrayList<>();
	List<String> l2 = new LinkedList<>();
	l1.add("Hello");  l1.add("World");
	l2.add("World");  l2.add("Hello");
	assert !l1.equals(l2);
	assert l1.hashCode() != l2.hashCode();  // probably

-- 
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ArrayList vs HashMap Roedy Green <inquiry@mindprod.com> - 2016-08-25 09:42 -0700
  Re: ArrayList vs HashMap Roedy Green <inquiry@mindprod.com> - 2016-08-25 09:43 -0700
    Re: ArrayList vs HashMap Eric Douglas <e.d.programmer@gmail.com> - 2016-08-25 10:06 -0700
      Re: ArrayList vs HashMap Roedy Green <inquiry@mindprod.com> - 2016-08-30 16:34 -0700
        Re: ArrayList vs HashMap Andreas Leitgeb <avl@logic.at> - 2016-08-31 12:55 +0000
          Re: ArrayList vs HashMap Eric Sosman <esosman@comcast-dot-net.invalid> - 2016-08-31 13:05 -0400
            Re: ArrayList vs HashMap Andreas Leitgeb <avl@logic.at> - 2016-08-31 17:34 +0000
  Re: ArrayList vs HashMap j4n bur53 <janburse@fastmail.fm> - 2016-08-31 09:15 +0200

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