Ravindra Ranwala's Blog

Introduction Lambda expressions are by far the most discussed and emphasized feature of Java 8. While I agree that Lambdas being the salient feature in Java8, still there are lot more new things hidden behind the shadows of lambda expressions. Today we gonna take a look at one of them, the CompletionStage API [1] for leveraging asynchronous programming. Java5 introduced the ExecutorService pattern where programmers can submit tasks to a pool of Threads. This yields a Future object and the only way to get the result from a future object is to call its get() method in the thread that submitted the task. This method is blocking, so this call will block the thread until the result is available to process. So, the use of  Future is ruled out on performance grounds. This is exactly where the CompletionStage comes to the rescue. [2] What Is a CompletionStage In a nutshell, a CompletionStage is a model that carries a task. A task can be an instance of Runnable, Consumer, or Functio...

Introduction Hardware trends drive programming idioms. The Java language has had support for threads and concurrency from day 1; the language includes synchronization primitives such as synchronized and volatile, and the class library includes classes such as Thread. However, the concurrency primitives that were sensible in 1995 reflected the hardware reality of the time: most commercially available systems provided no parallelism at all, and even the most expensive systems provided only limited parallelism. In those days, threads were used primarily for expressing asynchrony, not concurrency, and as a result, these mechanisms were generally adequate to the demands of the time. Going forward, the hardware trend is clear; Moore's Law will not be delivering higher clock rates, but instead delivering more cores per chip. As we enter the multi-core era, we will need to find finer-grained parallelism or risk keeping processors idle even though there is plenty of work to do. As the d...