Re: C# Hastable's equivalent in Java

From:

"Oliver Wong" <owong@castortech.com>

Newsgroups:

comp.lang.java.programmer,comp.lang.java.help

Date:

Fri, 28 Apr 2006 19:23:02 GMT

Message-ID:

<qYt4g.226$zn1.172@edtnps90>

"bugbear" <bugbear@trim_papermule.co.uk_trim> wrote in message
news:4451d5c3$0$2573$ed2619ec@ptn-nntp-reader02.plus.net...

Thomas Weidenfeller wrote:

[...]

I have to follow the same for my Java conversion. The
Hashtable in java.util does not work the same as C#.

They work very well. You just assume hashtables have a property which
they don't. If you want to get the exact same C# hashtable behavior, you
need to find out which hash functions are used there, and which algorithm
is used for the table, and reimplement a hashtable from scratch. In
theory, because if the original code really depends on the internal order
of a hashtable, it is badly broken and should be fixed first. There is
not much point in re-creating this design error in some other language.

If the ordering *is* essential, org.apache.commons.collections.OrderedMap
uses extra resources to maintain items in insertion order.

To agree (strongly) with Thomas, this does not "fix a bug"
in HashMap, it adds *extra* functionality.

The OP wrote:

<quote>
In the C# code that am working on, there is an arraylist and they are
copying the values to a hashtable for easy retrieval purpose. After
making a copy, ironically, the order of values in both the arraylist
and the hastable are different.
</quote>

So if maintaining the exact same behaviour as in C# is required, simply
maintaining items in insertion order will not do it.

- Oliver