java - ForkJoinPool，如何打印出每个工作线程的ID？

Question

我是 Java 的新手，正在尝试学习 fork/join 框架。我在网上看到下面的代码，但是，在我运行代码之后，输出似乎是乱序的。所以我只是想知道是否有任何方法可以打印出每个工作线程的 ID？输出非常困惑，没有 ID 来识别哪个线程在做什么。

来源::

public class MyRecursiveTask extends RecursiveTask<Long> {

    public static void main(String[] args) {
        MyRecursiveTask myRecursiveTask = new MyRecursiveTask(128);
        ForkJoinPool fjp1 = new ForkJoinPool();
        long mergedResult = fjp1.invoke(myRecursiveTask);



        System.out.println("mergedResult = " + mergedResult);
    }

    private long workLoad = 0;

    public MyRecursiveTask(long workLoad) {
        this.workLoad = workLoad;
    }

    protected Long compute() {

        //if work is above threshold, break tasks up into smaller tasks
        if (this.workLoad > 16) {
            System.out.println("Splitting workLoad : " + this.workLoad);

            List<MyRecursiveTask> subtasks
                    = new ArrayList<MyRecursiveTask>();
            subtasks.addAll(createSubtasks());

            for (MyRecursiveTask subtask : subtasks) {
                subtask.fork();
            }

            long result = 0;
            for (MyRecursiveTask subtask : subtasks) {
                result += subtask.join();
            }
            return result;

        } else {
            System.out.println("Doing workLoad myself: " + this.workLoad);
            return workLoad * 3;
        }
    }

    private List<MyRecursiveTask> createSubtasks() {
        List<MyRecursiveTask> subtasks
                = new ArrayList<MyRecursiveTask>();

        MyRecursiveTask subtask1 = new MyRecursiveTask(this.workLoad / 2);
        MyRecursiveTask subtask2 = new MyRecursiveTask(this.workLoad / 2);

        subtasks.add(subtask1);
        subtasks.add(subtask2);

        return subtasks;
    }
}

输出:

Splitting workLoad : 128
Splitting workLoad : 64
Splitting workLoad : 32
Splitting workLoad : 64
Doing workLoad myself: 16
Splitting workLoad : 32
Doing workLoad myself: 16
Doing workLoad myself: 16
Splitting workLoad : 32
Doing workLoad myself: 16
Doing workLoad myself: 16
Splitting workLoad : 32
Doing workLoad myself: 16
Doing workLoad myself: 16
Doing workLoad myself: 16
mergedResult = 384

Answer 1

compute() 是此任务执行的主要计算。您应该在此处放置用于获取线程 ID 的代码。修改你的 System.out.println 如下:

System.out.println("Splitting workLoad : "+ this.workLoad + "by thread "+ Thread.currentThread().getId());
System.out.println("Splitting workLoad : "+ this.workLoad + "by thread "+ Thread.currentThread().getId());

我的观点是，您应该使用线程名称 (Thread.currentThread().getName()) 而不是线程 ID。给线程名称我们比线程 id 更有意义。