Inception movie explained programmatically

The ThreadLocal class appeared with little fanfare in version 1.2 of the Java platform. While support for thread-local variables has long been a part of many threading facilities, such as the Posix pthreads facility, the initial design of the Java Threads API lacked this useful feature. Further, the initial implementation was quite inefficient. For these reasons, ThreadLocal gets relatively little attention, but it can be very handy for simplifying the development of thread-safe concurrent programs. In this third installment of Threading lightly, Java software consultant Brian Goetz examines ThreadLocal and offers tips for exploiting its power.

Contended synchronization, however, is quite expensive. Moreover, a high degree of contention is disastrous for scalability -- an application that had a high degree of contended synchronization will exhibit markedly worse performance as the load increases. This article will explore several techniques for reducing contention, and hence improving scalability, in your programs.

Unlike many other programming languages, the Java Language Specification included explicit support for threading and concurrency. While having language support for concurrency makes it easier to specify and manage constraints on shared data and the timing of operations across threads, it doesn't make the complexities of concurrent programming any easier to understand. This three-part series aims to help programmers understand some of the major issues behind multithreaded programming in the Java language, and in particular to understand the impact of thread safety on Java program performance.