Question

I have a multi-threaded application (a web app in Tomcat to be exact). In it there is a class that almost every thread will have its own instance of. In that class there is a section of code in one method that only ONE thread (user) can execute at a time. My research has led me to believe that what I need here is a mutex (which is a semaphore with a count of 1, it would seem).

So, after a bit more research, I think what I should do is the following. Of importance is to note that my lock Object is static.

Am I doing it correctly?

public Class MyClass {
  private static Object lock = new Object();
  public void myMethod() {
    // Stuff that multiple threads can execute simultaneously.
    synchronized(MyClass.lock) {
      // Stuff that only one thread may execute at a time.
    }
  }
}

Answer 1

In your code, myMethod may be executed in any thread, but only in one at a time. That means that there can never be two threads executing this method at the same time. I think that’s what you want – so: Yes.