How to parallelize java source codes for large data with Threadpool

Question

I try to parallelize some source code with ExecutorService and LinkedList in Java.

In the following source code, some process is done for each line of a text file.

When each line is relatively short, the following source code works well (all lines are read and processes are done).

However, when it is relatively long, the program stops reading a line without any errors.

Is there any capacity for LinkedList? Can I increase the capacity? Is there another proper way for parallelization?

        ExecutorService threadPool = Executors.newFixedThreadPool(4);
        Collection<Callable<Void>> processes = new LinkedList<Callable<Void>>();

        int c = 0;
        while ((string = br.readLine()) != null) {
            final String str = string;
            processes.add(new Callable<Void>() {
                @Override
                public Void call() {
                    // some process
                    return null;
                }
            });
        }

        try {
            threadPool.invokeAll(processes);
        } catch (InterruptedException e) {
            throw new RuntimeException(e);
        } finally {
            System.out.println("parallel finishes");
            threadPool.shutdown();
        }