For http://stackoverflow.com/questions/17243652/

    private int getOffset(int capacity, int items) {
        return ((getMaxCapacity() + 1) * items + capacity) * BLOCK_SIZE;
    }


    @Override
    public int getSolution(int capacity, int items) {
        if (items == syncsPassed ) {
            return previousItemSolutions[capacity];
        }
        ByteBuffer byteBuffer = ByteBuffer.allocate(BLOCK_SIZE);
        int offset = getOffset(capacity, items);
        try {
            FileChannel channel = cacheFile.getChannel();
            int readBytes = channel.read(byteBuffer, offset);

            System.out.println(readBytes);

            return byteBuffer.getInt();
        } catch (IOException e) {
            e.printStackTrace();
            close();
            throw new IllegalStateException(e);
        }
    }

    public void sync(int items) {
        checkTrue(items == syncsPassed,
                "Illegal sync: only " + syncsPassed + " rows were synchronized, but sync is called for row " + items);
        try {
            int offset = getOffset(0, items);
            FileChannel channel = cacheFile.getChannel().position(offset);
            IntBuffer buffer = IntBuffer.wrap(currentItemSolutions);
            ByteBuffer byteBuffer = ByteBuffer.allocate(currentItemSolutions.length * BLOCK_SIZE);
            byteBuffer.asIntBuffer().put(buffer);
            channel.write(byteBuffer);
            channel.force(false);
        } catch (IOException e) {
            close();
            throw new RuntimeException(e);
        }
        this.previousItemSolutions = this.currentItemSolutions.clone();
        this.currentItemSolutions = new int[getMaxCapacity() + 1];
        syncsPassed++;
    }