CODEWITHSUNDEEP
javasearcharraylist
Null Pointer
Null Pointer

Reputation: 275

Most efficient and quick search over Array List

I am trying to iterate over an ArrayList and want to find out an element. In list thousand of items are there so its taking much time to find. So, Can any one please suggest efficient and quick search. Code is below:

private FoodItem getFoodItem(List<FoodItem> foodItemList, String foodItemId) {
    if (foodItemId == null || foodItemList == null || foodItemList.isEmpty()) {
        return null;
    }
    for (FoodItem foodItem : foodItemList) {
        if (foodItem == null) {
            continue;
        }
        if (foodItem.getId().equals(foodItemId)) {
            return foodItem;
        }
    }
    return null;
}

Upvotes: 0

Views: 192

Answers (3)

dehasi
dehasi

Reputation: 2773

Probably parallel stream will help

foodItemList.parallelStream().findAny(foodItem->foodItem.getId().equals(foodItemId))

It returns Optional<FoodItem>

Upvotes: 0

Lino
Lino

Reputation: 19926

As already mentioned by @Eran in the comments. The use of a Map might be the best option, regarding the look up with the Id.

For conversion from a List to a Map you can make use of the Java8 Stream API:

Map<String, FoodItem> map = foodList.stream()
    .collect(Collectors.toMap(FoodList::getId, Function.identity());

Note: this should be done once and not for every lookup.

And then with the lookup:

public FoodItem getFoodItem(Map<String, FoodItem> map, String foodItemId){
    if (foodItemId == null || foodItemList == null || foodItemList.isEmpty()) {
        return null;
    }
    return map.get(foodItemId); // returns null if it doesn't exists
}

Upvotes: 1

BiS
BiS

Reputation: 503

If you NEED to have a List, you probably want it to be ordered on insertion time (depending on how many inserts vs search you perform, because ordered insert is slower of course) and then perform some binary search.

Or even better, use a HashMap if you don't need a list (or even, a LinkedHashMap if you need predictable order).

Upvotes: 0

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