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Date: Thu, 24 Jan 2002 22:28:29 +0000 (GMT)
From: =?iso-8859-1?q?Janek=20Bogucki?= <janekdb@yahoo.co.uk>
Subject: SequencedHashMap: This class is thread-safe (was Re: Silly Question)
To: Jakarta Commons Developers List <commons-dev@jakarta.apache.org>
In-Reply-To: <3C5072C9.C0F43363@collab.net>
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Hi John,

 --- John McNally <jmcnally@collab.net> wrote: > > 
> Remove the "This class is thread-safe" declaration
> in SequencedHashMap.

When I first read this class through I thought I'd
spotted a race condition in freshenSequence but a
rethink convinced me it was not thread-unsafe. Am I
wrong here? If not, what's the actual location of the
non thread-safe behaviour?

-Janek

    /**
     * Freshens the sequence of the element
<code>value</code> if
     * <code>value</code> is not <code>null</code>.
     *
     * @param key   The key whose sequence to freshen.
     * @param value The value whose existance to check
before removing the old
     *              key sequence.
     */
    protected void freshenSequence(Object key, Object
value)
    {
        if (value != null)
        {
            // Freshening existing element's sequence.
            keySequence.remove(key);
        }
        keySequence.add(key);
    }

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