用于读取.txt的多线程BufferedReader

Question

I'm wanting to read the line of a .txt do the task, and move on to the next line.

To make the program quicker, I want to multi-thread so each thread tries a line.

The problem is, I don't want the thread 1 trying the same line as thread 2.

Any ideas?

Answer 1

I suggest you have one thread doing all the reading, then put the lines into a producer/consumer queue (eg a LinkedBlockingQueue ) - you can then have multiple threads servicing that queue as consumers.

You really don't want multiple threads performing IO here - even if you had multiple independent BufferedReaders , if you're reading from traditional disks you don't want to end up seeking in multiple places. A producer/consumer queue separates the reading from the handling fairly simply - and makes it easier to test each part in isolation as well.

Answer 2

You can read the lines in one thread and dispatch a worker thread for each line:

try (BufferedReader reader = new BufferedReader(new FileReader("my.txt"))) {
   String line;
   while ((line = reader.readLine()) != null) {
     new Runnable() {
        void run() {
           // do stuff with line
        }
     }.run();
   }
}

Answer 3

I have an idea on what you are trying to achieve but not sure how you will code it. If you can make each thread work on a different set of lines then the threads will not clash. I mean let thread1 read from 1 to 100, thread2 read from 101 to 200 and so on. At the end join the results of all the threads to get the final result. Maybe a Fork/Join operation.

But @Jon comment makes me wary of following such an approach.

"You really don't want multiple threads performing IO here - even if you had multiple independent BufferedReaders, if you're reading from traditional disks you don't want to end up seeking in multiple places..