Java: CSV file read & write

Question

I'm reading 2 csv files: store_inventory & new_acquisitions.
I want to be able to compare the store_inventory csv file with new_acquisitions. 1) If the item names match just update the quantity in store_inventory. 2) If new_acquisitions has a new item that does not exist in store_inventory, then add it to the store_inventory.

Here is what i have done so far but its not very good. I added comments where i need to add taks 1 & 2.
Any advice or code to do the above tasks would be great! thanks.

    File new_acq = new File("/src/test/new_acquisitions.csv");
    Scanner acq_scan = null;
    try {
        acq_scan = new Scanner(new_acq);
    } catch (FileNotFoundException ex) {
        Logger.getLogger(mainpage.class.getName()).log(Level.SEVERE, null, ex);
    }
    String itemName;
    int quantity;
    Double cost;
    Double price;

    File store_inv = new File("/src/test/store_inventory.csv");
    Scanner invscan = null;
    try {
        invscan = new Scanner(store_inv);
    } catch (FileNotFoundException ex) {
        Logger.getLogger(mainpage.class.getName()).log(Level.SEVERE, null, ex);
    }
    String itemNameInv;
    int quantityInv;
    Double costInv;
    Double priceInv;


    while (acq_scan.hasNext()) {
        String line = acq_scan.nextLine();
        if (line.charAt(0) == '#') {
            continue;
        }
        String[] split = line.split(",");

        itemName = split[0];
        quantity = Integer.parseInt(split[1]);
        cost = Double.parseDouble(split[2]);
        price = Double.parseDouble(split[3]);


        while(invscan.hasNext()) {
            String line2 = invscan.nextLine();
            if (line2.charAt(0) == '#') {
                continue;
            }
            String[] split2 = line2.split(",");

            itemNameInv = split2[0];
            quantityInv = Integer.parseInt(split2[1]);
            costInv = Double.parseDouble(split2[2]);
            priceInv = Double.parseDouble(split2[3]);


            if(itemName == itemNameInv) {
                //update quantity

            }
        }
        //add new entry into csv file

     }

Thanks again for any help. =]

Answer 1

Your implementation makes the common mistake of breaking the line on commas by using line.split(","). This does not work because the values themselves might have commas in them. If that happens, the value must be quoted, and you need to ignore commas within the quotes. The split method can not do this -- I see this mistake a lot.

Here is the source of an implementation that does it correctly: http://agiletribe.wordpress.com/2012/11/23/the-only-class-you-need-for-csv-files/