Re: synchronization is not working right between two copies of the same class for member function

From:
Patricia Shanahan <pats@acm.org>
Newsgroups:
comp.lang.java.programmer
Date:
Sat, 25 Nov 2006 22:44:21 GMT
Message-ID:
<9H3ah.3449$tM1.1087@newsread1.news.pas.earthlink.net>
John T. Kerich wrote:

I have a global class that was created to hold the references to different
classes and global variables. This global class is initialized by the main
class (some variable are pass in as arguments) and all the other threads do
a "gd = new Global()" to get their own copy of the class (this should be
done by the threads after initialization was done by main). The idea was

....

static boolean active = false;

void synchronized connect() {
while (active) {
    wait(50);
}
active = true;
member code
active = false;
}

....

A synchronized member method, such as connect(), is synchronized on
"this". Since each thread has its own Global, each synchronizes on a
different object.

You need to synchronize on something for which there is one object for
the whole class. Here are some options:

1. Synchronize on Global.class.

2. Make active a Boolean, and synchronize on active.

3. Create an artificial, static, activeLock object and synchronize on it.

Patricia

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