Possible to sum up object values in HashMap?

Question

I've just started using HashMaps in Java, and I was wondering if it's possible to sum up the object values in the HashMap.

I've already done this using an ArrayList like so:

private int totalWeight() {
        int totalWeight = 0;
        for(Item item : items){
            totalWeight += item.getWeight();
        }
        return totalWeight;
    }

I have different objects with the value weight, and I'm trying to return the total value of the weight as totalWeight, but can't seem to do so using HashMap.

Can you show us a snippet where you are trying to use a map? — marko, Mar 17 '15 at 20:36
Grab the values using `map.values()`, then loop through them like you did the list — Vince, Mar 17 '15 at 20:36

score 0 · Accepted Answer · answered Mar 17 '15 at 20:42

You can try something like this

public class HMTest {

    public static void main(String[] args) {

        int totalWeight = 0;
        HashMap<String, Item> map = new HashMap<String, Item>();
        map.put("Key1", new Item(10));
        map.put("Key2", new Item(20));
        map.put("Key3", new Item(30));

        Collection<Item> values = map.values();

        for (Item i : values) {
            totalWeight += i.getWeight();
        }

        System.out.println("Total Weight :" + totalWeight);

    }

}

class Item {
    private int weight;

    public Item(int weight) {
        this.weight = weight;
    }

    public int getWeight() {
        return weight;
    }

    public void setWeight(int weight) {
        this.weight = weight;
    }

}

This seemed to work nicely! Thanks a lot!! – Wangensteen Mar 17 '15 at 21:22 — Wangensteen, Mar 17 '15 at 21:22

Possible to sum up object values in HashMap?

1 Answers1