Blog for Shendy

Blog for Shendy

Arrays.asList(array) Won't Not Give You ArrayList, Here is Why?

Arrays.asList(array) Won't Not Give You ArrayList, Here is Why?

Whenever you have a primitive array and you would like to convert it to List (collection-based array). You might do this using asList() method of Arrays class of Collections framework. But this doesn't result to ArrayList, instead to an implementation of List with added feature of not being resizable, and still honoring all of the other methods in the interface.

Let's demonstrate by an example:

1: String[] array = {"Cat", "Dog"};                    // [Cat, Dog]
2: List<String> list = Arrays.asList(array);           // returns fixed size list
3: list.set(1, "Lion");                                // [Cat, Lion]
4: array[0] = "Fox";                                   // [Fox, Lion]
5: String[] array2 = (String[]) list.toArray();        // [Fox, Lion]
6: list.remove(1);                        // throws UnsupportedOperationException

Line 3 and 4 show that you can change elements in either array or the list.

Line 6 shows that list is not resizable, because it is backed by the underlying array.

That's all for this InfoSnippet.

Let me know if you have questions.

#array
 
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