The Mutex and Lock Management

Abstract

In the previous two chapters, I focused on the pitfalls of writing multithreaded applications in Java. With this chapter, I’ll show you a few solutions to the problems. I’ll start out with a look at a roll-your-own mutex class that is easier to use than synchronized in some situations. In particular, it allows you to specify a timeout so that you won’t have to wait forever to acquire a lock (as compared to synchronized, which provides no timeout facility). We’ll also look at a lock manager class that lets you safely acquire multiple semaphores without deadlocking. Using objects of these classes rather than the built-in synchronized can save you hours of searching for unexpected deadlocks, and though these classes don’t solve every possible deadlock problem, they’re still pretty useful.