Re: Preventing Memory Leak when using HashMap

From:

Daniel Pitts <newsgroup.spamfilter@virtualinfinity.net>

Newsgroups:

comp.lang.java.programmer

Date:

Fri, 12 Feb 2010 15:10:43 -0800

Message-ID:

<Ldldn.6731$YR1.4222@newsfe17.iad>

On 2/11/2010 8:18 AM, markspace wrote:

Krist wrote:

So, both class has local variable with (a coincidence) same name.

This will not be GCed, isn't it ? I read anywhere that unremoved
HashMap is one of the factor of Java memory leak.

If the HashMap becomes unreachable, it will be garbage collected. A
HashMap only "leaks" when you have a reference to the HashMap you want
to keep, and you want to remove a reference inside the hash map. In
fact, I believe this problem only really occurs when you have a
WeakHashMap, which can accidentally hold on to it's own references.

That makes no sense...
A WeakHashMap uses WeakReferences as entries, which allows the GC to
garbage collect the values referenced. Any object is free to hold a
reference to itself without affecting GC. The only requirement for GC
eligibility is that the object itself isn't accessible through any stack
(directly or indirectly). Reference count is not at all a test.
--
Daniel Pitts' Tech Blog: <http://virtualinfinity.net/wordpress/>