Btukfyl

I was trying to implement a java program to read a huge file simultaneously by 100 threads.
So I am dividing my file in 100 chunks and giving it to 100 threads.
And at the end I want to calculate the capacity of each chunk and and print the total capacity read by all threads.

Below is my code...
And I am getting errors in my code and I am not able to fix it. I am new to concurrency and Multithreading .Please help me to understand and fix this issue.

public class CustomRecursiveTaskToReadHugeFile extends RecursiveTask {

    static volatile boolean flag;

    File file;

    FileChannel fc;

    BlockingQueue<Integer> bq;

    public CustomRecursiveTaskToReadHugeFile(boolean flag, File file, FileChannel c) {

        super();

        this.flag = flag;

        this.file = file;

        this.fc = c;

    }



    @Override

    protected Integer compute() {

        if (!flag) {

             return ForkJoinTask.invokeAll(createSubtasks()).stream().mapToInt(ForkJoinTask::join).sum();  // Here is the problem area

        } else

            processFiles();

    }



    private Collection<CustomRecursiveTaskToReadHugeFile> createSubtasks() {

        List<CustomRecursiveTaskToReadHugeFile> cl = new ArrayList<CustomRecursiveTaskToReadHugeFile>();



        if (!flag) {

            FileInputStream is = null;

            try {

                is = new FileInputStream(file);

            } catch (FileNotFoundException e) {

                e.printStackTrace();

            }

            FileChannel c = is.getChannel();

            for (long i = 0; i < 1000000; i = i + 100) {

                try {

                    c.position(i);

                    cl.add(new CustomRecursiveTaskToReadHugeFile(flag, file, c));

                } catch (IOException e) {

                    e.printStackTrace();

                }

            }

        }

        return  cl;

    }



    private  Integer processFiles() {

        ByteBuffer dst = null;

        for (int i = 0; i < 00; i++) {

            try {

                fc.read(dst, i);



            } catch (IOException e) {

                e.printStackTrace();

            }

        }

        System.out.println(" Current thread capacity is " + dst.capacity());

        try {

            bq.put( new Integer(dst.capacity()));

        } catch (InterruptedException e) {

            e.printStackTrace();

        }



        return new Integer(dst.capacity());



    }

}