多线程之ForkJoinPool

原理

ForkJoinPool是jdk7新加的用法，它的优势在于充分的利用cpu，采用工作窃取算法,将一个大任务根据阈值分割成很多个子任务,最后根据场景是否要合并子任务运算结果。

构造

public ForkJoinPool() {
        this(Math.min(MAX_CAP, Runtime.getRuntime().availableProcessors()),
             defaultForkJoinWorkerThreadFactory, null, false);
    }
    
public ForkJoinPool(int parallelism,
                        ForkJoinWorkerThreadFactory factory,
                        UncaughtExceptionHandler handler,
                        boolean asyncMode) {
        this(checkParallelism(parallelism),
             checkFactory(factory),
             handler,
             asyncMode ? FIFO_QUEUE : LIFO_QUEUE,
             "ForkJoinPool-" + nextPoolId() + "-worker-");
        checkPermission();
    }

根据是否需要合并子任务运算结果,任务需要继承抽象类RecursiveAction,RecursiveTask<V>,后者为需要合并子任务结果,泛型为结果类型;