CODEWITHSUNDEEP
javaarrayslistcastingtype-conversion
User
User

Reputation: 4211

Array to List or List to Array, which conversion is faster?

In java, basically these two conversions are so common and popular...

So the question is, which is faster, Array to List or its reverse?

Now, Why am I asking this question? Because I've to implement a method in which an array or a list, both can be passed in parameter. I just have to iterate this list and that's all. So here I have to decide that what should I convert? array to list or list to array!

Upvotes: 5

Views: 4034

Answers (3)

ssaa
ssaa

Reputation: 1112

Arrays.asList will faster since it doesnt have to copy any data instead it has to just pack it.

Upvotes: 1

Serge Ballesta
Serge Ballesta

Reputation: 148910

IMHO, you are handling the rod the wrong side. The good question to ask is whether you need an array or List in your method. By the way, List it just an interface, and many implementations could exist. For example the JDK directly provides ArrayList which is backed by an array, so conversion to array should be fast, and LinkedList which is a doubly linked implementation, and many others including abstract classes intended to help for custom implementations.

In short, you know how you want to use the elements in your method, so just use the more appropriate container.

In my opininion, if you intend to iterate the elements, use a List, if you need intensive random access and could receive an linked list implementation, then use an Array.

Upvotes: 0

yole
yole

Reputation: 97168

Arrays.asList is faster because it does not copy data - it returns an object wrapping the array passed to it, and implementing the List interface. Collection.toArray() copies the data to the array, so it runs in O(N) instead of O(1).

Upvotes: 17

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