正进一步

public class  extends RecursiveTask<Long> {
    private File file;
    private (File f){
        this.file = f;
    }
    
    protected Long compute() {
        if(file.isFile()){
            System.out.println(file.getAbsolutePath());
            return file.length();
        }
        List<MyTask>  tasks =new ArrayList<>();
        File[] files = file.listFiles();
        for(File f : files){
            MyTask task = new MyTask(f);
            
            task.fork();
            tasks.add(task);
        }
        long size = 0;
        for(MyTask myTask: tasks){
            size = size+myTask.join();
        }
        return size;
    }
    public static void main(String[] args) {
        ForkJoinPool pool =new ForkJoinPool();
        try{
            Long length  =pool.invoke(new MyTask(new File("/Users/zheng/Documents/mt_workspace/")));
            System.out.println("得到的文件大小为"+ length);
        }catch (Exception ex){
            ex.printStackTrace();
        }finally {
            pool.shutdown();
        }
    }
    
}