Using Arrays.asList with int array

Question

Using java.util.Arrays.asList, why its shows different list size for int (Primitive type) and String array?

a) With int

Answer 1

List cannot hold primitive values because of java generics (see similar question). So when you call Arrays.asList(ar) the Arrays creates a list with exactly one item - the int array ar.

EDIT:

Result of Arrays.asList(ar) will be a List<int[]>, NOT List<int> and it will hold one item which is the array of ints:

[ [1,2,3,4,5] ]

You cannot access the primitive ints from the list itself. You would have to access it like this:

list.get(0).get(0) // returns 1
list.get(0).get(1) // returns 2
...

And I think that's not what you wanted.

Answer 2

List is a generic type, primitive types are not valid substitutes for the type parameter.

So in your first example when you call Arrays.asList() with an int[], the value for the type parameter will be int[] and not int, and it will return a list of int arrays. It will have only 1 element, the array itself.

The second case will be a List<String>, properly holding the 4 strings which you pass to it.