How to convert List to a HashMap

Question

How can I convert this:

Map<String, Integer> itemsBought

So that I can add it on the ArrayList as Follows:

public void add(String prd, int qty){
        orderList.add(new Order(prd, qty));
}

Are there other solutions beside this:

hashMap.keySet().toArray(); 
hashMap.values().toArray();

Thank you in advance.

Tarlog · Accepted Answer · 2011-05-11 17:32:41Z

11

for (Entry<String, Integer> entry : itemsBought.entrySet()) {
    orderList.add(new Order(entry.getKey(), entry.getValue()));
}

answered May 11, 2011 at 17:32

Tarlog

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Comments

Rangi Lin · Accepted Answer · 2011-05-11 17:40:19Z

1

for (String product : itemsBought.keySet()) {
    int quantity = itemsBought.get(product);
    orderList.add(new Order(product, quantity));
}

I prefer more readability (not much though)

answered May 11, 2011 at 17:40

Rangi Lin

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2 Comments

mre Over a year ago

L Regardless of implementation, it is clearly demonstrated by Tarlog's answer that you must iterate the collection in order to populate the ArrayList. That being said, I don't see any value in this answer.

Jochen Bedersdorfer Over a year ago

This solution does a map lookup for each key (which might be O(n) worst case, depending on implementation, looking at O(2n)). The first solution, again dependent on the implementation, might simply loop through all entries in O(n) total. For trivial map sizes this is completely irrelevant though.

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