Java: CSV file read & write.

Question

Im reading in 2 csv file: 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.

Heres what i have 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 2 taks 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

Suggest you use one of the existing CSV parser such as Commons CSV or Super CSV instead of reinventing the wheel. Should make your life a lot easier.

Answer 2

The operation you are performing will require that for each item in your new acquisitions, you will need to search each item in inventory for a match. This is not only not efficient, but the scanner that you have set up for your inventory file would need to be reset after each item.

I would suggest that you add your new acquisitions and your inventory to collections and then iterate over your new acquisitions and look up the new item in your inventory collection. If the item exists, update the item. If it doesnt, add it to the inventory collection. For this activity, it might be good to write a simple class to contain an inventory item. It could be used for both the new acquisitions and for the inventory. For a fast lookup, I would suggest that you use HashSet or HashMap for your inventory collection.

At the end of the process, dont forget to persist the changes to your inventory file.