Introduction By default, ForkJoinPool creates a thread for each processor, and parallelStream will use this shared thread pool to submit tasks if not specified.
So how do we handle a specific situation where we want to use a custom ForkJoinPool?
Common operations If we want to do an addition from 1 to 1000, we can use parallel stream like this.
List<Integer> integerList= IntStream.range(1,1000).boxed().collect(Collectors.toList()); ForkJoinPool customThreadPool = new ForkJoinPool(4); Integer total= integerList.
Preface In Java, threads are the counterpart of system threads and are used to handle a range of system resources. The number of threads that can be opened is limited in both windows and linux, so if you create unlimited threads in your java program, you will encounter a situation where no threads can be created.
CPU cores are limited and if there are multiple threads running at the same time, the CPU will rotate according to the priority of the threads and allocate a specific amount of CPU time to each thread.
The use of Future in java Future is an interface introduced in java 1.5 that can be used to get asynchronous results easily. This article will explain how to use Future through specific examples.
Creating Future As mentioned above, Future represents the result of asynchronous execution, which means that when the asynchronous execution is finished, the returned result will be saved in Future.
So when do we use Future? Generally speaking, when we execute a long-running task, using Future allows us to temporarily deal with other tasks, and then return the result when the long task is finished.
Introduction This article combines the JUC package provided by Doug Lea in JDK1.5 to understand the use of thread pools from the setting of thread pool size parameters, the creation of work threads, the recycling of idle threads, the use of blocking queues, task rejection strategies, thread pool Hook and other aspects, which involves some details including the choice of different parameters, different queues, different rejection strategies, the resulting The details include the different parameters, the different queues, the choice of different rejection strategies, the resulting impact and behavior, and for better use of the thread pool.
Estimating Throughput Now there is a task which execution time is divided into 2 parts, the first part does math and the second part waits for IO. these two parts are called compute operation and wait operation.
So now we need to estimate the peak throughput that can be achieved by executing this task with the CPU at full power.
Then we need to know how much time it takes to execute this task, how much time is spent on the computation part and how much time is spent on the wait part.
Preface When it comes to java thread pools nothing is more familiar than the ExecutorService interface. jdk1.5 adds java.util.concurrent package under this api, which greatly simplifies the development of multi-threaded code. Whether you use FixedThreadPool or CachedThreadPool the implementation behind it is ThreadPoolExecutor. threadPoolExecutor is a typical product of cache pooling design, because the pool has a size, when the pool volume is not enough to carry, it involves a rejection policy.
