Question

I have two List of array string. I want to be able to create a New List (newList) by combining the 2 lists. But it must meet these 3 conditions:

1) Copy the contents of store_inventory into newList.

2) Then if the item names in store_inventory & new_acquisitions match, just add the two quantities together and change it in newList.

3) If new_acquisitions has a new item that does not exist in store_inventory, then add it to the newList.

The titles for the CSV list are: Item Name, Quantity, Cost, Price.

The List contains an string[] of item name, quantity, cost and price for each row.

    CSVReader from = new CSVReader(new FileReader("/test/new_acquisitions.csv"));
    List <String[]> acquisitions = from.readAll();

    CSVReader to = new CSVReader(new FileReader("/test/store_inventory.csv"));
    List <String[]> inventory = to.readAll();

    List <String[]> newList;

Any code to get me started would be great! =]

this is what i have so far…

        for (int i = 0; i < acquisitions.size(); i++) {
        temp1 = acquisitions.get(i);
        for (int j = 1; j < inventory.size(); j++) {
            temp2 = inventory.get(j);
            if (temp1[0].equals(temp2[0])) {
                //if match found... do something?



                //break out of loop
            }
        }
        //if new item found... do something?
    }

Answer 1

I would start by building the newList as a HashMap or TreeMap instead of a List. This makes it easy to search for the matching record. Furthermore, I would convert the String[] to a custom object (e.g. Record) that contains the name, quantity, cost and price field. This would take care of copying the information. The you could try something like this:

Map<String, Record> newMap = new TreeMap<String, Record>();
for(String[] ss : acquisitions) {
    Record rec = Record.parse(ss); // For requirement (1)
    newMap.put(rec.getName(), rec);
}

for(String[] ss : inventory) {
    Record rec = Record.parse(ss); // For requirement (1)
    if(newMap.containsKey(rec.getName())) {
        // For requirement (2)
        // The mergeWith method can then add quantities together
        newMap.get(rec.getName()).mergeWith(rec);
    } else {
        // For requirement (3)
        newMap.put(rec.getName(), rec);
    }
}

edit
An extra advantage of having a Record object, is that it can be printed to screen much easier by implementing the toString function.

public class Record implements Comparable<Record> {
    public static Record parse(String[] ss) {
        // TODO: implement some basic parsing
    }

    private String name;
    private int quantity;
    private BigDecimal cost, price;

    private Record() {}

    public String getName() { return name; }
    public int getQuantity() { return quantity; }
    public BigDecimal getCost() { return cost; }
    public BigDecimal getPrice() { return price; }

    public int compareTo(Record other) {
        return this.name.compareTo(other.name);
    }

    public String toString() {
        return name;
    }
}