Duplicate elements in ArrayList

Question

I have two array list, One is to save name and other is to save quantity. I want to avoid duplicate in the array list. Name array list contains name and its corresponding quantity is contained in quantity array list.

My array list can contains duplicate names, I want to traverse array list to check the name if already exists, if it exists then add the quantity to the previous value and delete duplicate entry.

Eg

Name     Quantity
ABC      20
xyz      10
ABC      15

Output Required

Name    Quantity
ABC      35
XYZ      10

Thanks

Solution

You should use a Map instead, which will not allow for duplicate entries. You use it something like this:

Map<String, Integer> nameToQuantityMap = new HashMap<String, Integer>():

nameToQuantityMap.put("Mr Smith", 100);
nameToQuantityMap.put("Mrs Jones", 500);

EDIT: Now that you've edited the question, the answer is different. If you want to add the values of duplicate keys, you'll have to do something like this:

// For each (name, quantity) pair
if (nameToQuantityMap.containsKey(name) ) {
    Integer sum = nameToQuantityMap.get(name) + quantity;
    nameToQuantityMap.put(name, sum);
}
else {
        nameToQuantityMap.put(name, quantity);
}

Comments

[devrobf]

Previously you said you wanted to delete the old entry, now you are adding them. Which is it?