Computers

Though many Java books and articles recommend double-checked locking, unfortunately, it is not guaranteed to work in Java.

Many authors advocate the double-checked locking idiom to access a Singleton object in an intuitively thread-safe way. Unfortunately, for counterintuitive reasons, double-checked locking doesn't work in Java.

Discussion of two more architectural solutions to threading problems: a synchronous dispatcher (or 'reactor') and an asynchronous dispatcher (or 'active object').

Discusses architectural solutions to threading problems. Takes a look at threads from the perspective of an object-oriented designer, and at how to implement threads in an object-oriented environment, focusing on the implementation of asynchronous methods.

Reader/writer locks let multiple threads safely access a shared resource in an efficient way.

How to implement the Observer pattern (used by AWT/Swing for its event model) in a multithreaded environment.

Timers let you perform fixed-interval operations, such as animation refreshes.

A condition variable adds to wait the ability to not wait when the condition you're waiting for has already taken place; and a counting semaphore lets you control a pool of resources without sucking up machine cycles in polling loops.

Presents two approaches to creating thread-safe singletons.

Looks at how and why you might want to roll your own exclusion semaphores, and presents a lock manager that will help you safely acquire multiple semaphores.

Discusses the perils that can arise when you approach multithreading in a naive way.

Discusses the things you need to know to program threads in the real world. This article assumes you understand the language-level support for threads and focuses on the legion of problems that arise when you try to use these language features.

In this article, Brian Goetz looks at some of the commonly proposed fixes and shows how each of them fails to render the DCL idiom thread-safe under the Java Memory Model.

Details on the reasons - some very subtle - why double-checked locking cannot be relied upon to be safe. Signed by a number of experts, including Sun engineers.

Explains how to apply consistent rules for acquiring multiple locks simultaneously, to reduce the likelihood of synchronization deadlocks.

Explains how to fix the double-checked locking idiom by using thread-local variables and takes a look at its performance.

Gives an introduction to threads and explores the Thread class and runnables.

Explains synchronization, Java's synchronization mechanism, and two problems that arise when developers fail to use that mechanism correctly.

Explains how priority relates to thread scheduling and how to use the wait/notify mechanism to coordinate the activities of multiple threads.

Focuses on thread groups, volatility, thread-local variables, timers, and the ThreadDeath class. Also describes how various thread concepts combine to finalize objects.

Examines ThreadLocal and offers tips for exploiting its power. By Brian Goetz.

Explains why contended synchronization is a problem and then explores several techniques for reducing contention, and hence improving scalability.

Takes a look at the semantics and the performance penalty of Java's synchronized keyword. By Brian Goetz.

Lab. manual by Astha Ekadiyanto.

A course covering all aspects of multi-thread programming in Java from plain synchronization over Java 5.0 concurrency utilities to memory model issues.

The thread gate pattern is an effective tool for managing thread concurrency, but not many developers know about it. Introduces the concept of thread gates, and then shows how to implement them in a multithreaded prime-number generator.

An article covering Java thread basics.