public static String[] generateInitialData(final int accountsNumber, final int transferNumber) {
            List<Future<String>> futures = new ArrayList<>();
            ExecutorService threadPool = Executors.newFixedThreadPool(2);
            futures.add(threadPool.submit(new Callable<String>() {

                @Override
                public String call() throws Exception {
                    StringBuilder builder = new StringBuilder(1_000_000);
                    ThreadLocalRandom random = ThreadLocalRandom.current();
                    builder.append(accountsNumber);
                    for (int i = 0; i < accountsNumber; i++) {
                        builder.append(' ').append(random.nextInt(0, DEFAULT_BALANCE_BOUND));
                    }

                    return builder.toString();
                }
            }));
            futures.add(threadPool.submit(new Callable<String>() {

                @Override
                public String call() throws Exception {
                    StringBuilder builder = new StringBuilder(10_000_000);
                    ThreadLocalRandom random = ThreadLocalRandom.current();
                    builder.append(transferNumber);
                    for (int i = 0; i < transferNumber; i++) {
                        builder.append(' ').append( random.nextInt(0, accountsNumber) ).
                                append(' ').append( random.nextInt(0, accountsNumber) ).
                                append(' ').append( random.nextInt(0, TRANSFER_AMOUNT_BOUND) );
                    }

                    return builder.toString();
                }
            }));

            threadPool.shutdownNow();
            final String[] result = new String[futures.size()];
            for (int i = 0; i < futures.size(); i++){
                try {
                    result[i] = futures.get(i).get();
                } catch (InterruptedException | ExecutionException e) {
                    e.printStackTrace();
                }
            }

            return result;
        }