Converting a List type<Integer> to String[] Array using method reference

Question

I am trying to convert a List of type Integer to an Array of Strings. I want to do it using the method reference passed to toArray() as below, which must work somehow since my CS professor showed this to us in class.

     List<Integer> strawberry = IntStream.rangeClosed(1, 100)
             .boxed().collect(Collectors.toList());

     String[] plum = strawberry.toArray(String[]::new);

However I got the following error message:

Exception in thread "main" java.lang.ArrayStoreException: arraycopy: element type mismatch: can not cast one of the elements of java.lang.Object[] to the type of the destination array, java.lang.String at java.base/java.lang.System.arraycopy(Native Method)

How can this be fixed?

I know there are easier ways of doing this, but I want to learn how to use this method correctly. Thanks.

Answer 1

You need to first map to a string stream:

String[] plum = strawberry.stream()
            .map(String::valueOf)
            .toArray(String[]::new);

But you can do both in one step:

String[] plum = IntStream.rangeClosed(1, 100)
         .mapToObj(String::valueOf)
         .toArray(String[]::new);

Answer 2

One you need both stream and valueOf from `String:

List<Integer> strawberry = IntStream.rangeClosed(1, 100)
        .boxed().collect(Collectors.toList());

String[] plum = strawberry.stream().map(String::valueOf).toArray(String[]::new);