I get it ... I think. It's OK to have local vars in my static methods, for
example:
public static String getReferringScreen(HttpServletRequest req)
{
String referringScreen = req.getHeader("Referer");
String reqScreenName = "";
if (referringScreen != null)
{
int pos1 = referringScreen.lastIndexOf("/");
int pos2 = referringScreen.lastIndexOf(".");
if (pos1 != -1 && pos2 != -1 && pos2 > pos1)
reqScreenName = referringScreen.substring(pos1 + 1, pos2);
}
return reqScreenName;
}
This method is thread safe too ? The only issues would be with static
methods that utilize static vars ?
Thanks in advance ...
-----Original Message-----
From: Milt Epstein [mailto:[EMAIL PROTECTED]]
Sent: Tuesday, November 13, 2001 3:59 PM
To: [EMAIL PROTECTED]
Subject: Re: Utility class and multi-threaded servlets
On Tue, 13 Nov 2001, Peters, Jim wrote:
> I searched the archives for an answer to my question, but did not see one
> posed exactly like mine.
>
> I am developing a multi-threaded servlet app, and have developed a utility
> class (all static methods) that all the servlets use.
> For example:
>
> public class Utility
> {
> public static String convertDouble(double val)
> {
> NumberFormat nf = NumberFormat.getInstance();
> nf.setMaximumFractionDigits(2);
> nf.setMinimumFractionDigits(2);
> return nf.format(val);
> }
> }
>
> The above is used in my servlets by invoking the method in this manner:
>
> String str = Utility.convertDouble(setUp);
>
> My question is this ... Do I have to synchronize the static methods in my
> Utility class ? Will one thread stomp on another one in the event that
> multiple are executing the code at the same time ?
>
> I suspect the answer is yes but I am also worried about all the threads
> waiting for synchronized methods.
[ ... ]
The answer is, it depends. That is, it depends on how the particular
methods are written. There is nothing inherent about static methods
that would require synchronization (i.e., they are not inherently
thread-safe or thread-safe). The particular method you have above
would not need to be synchronized -- the key point perhaps is that nf
is local to the method. Now if nf had been a static class variable
(and some of the other methods also manipulated nf as convertDouble
does), then you would have a potential synchronization problem. So
really this has to be looked at like any threading issue, the fact
that static methods are involved really doesn't make a difference.
Milt Epstein
Research Programmer
Software/Systems Development Group
Computing and Communications Services Office (CCSO)
University of Illinois at Urbana-Champaign (UIUC)
[EMAIL PROTECTED]
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