Print distinct from the Array Stream in Java 8 - java-8

Question

How to print the distinct element from the Array Stream in java 8?
I am playing with Java-8 and trying to understand how it works with distinct.
Collection<String> list = Arrays.asList("A", "B", "C", "D", "A", "B", "C");
// Get collection without duplicate i.e. distinct only
List<String> distinctElements = list.stream().distinct().collect(Collectors.toList());
//Let's verify distinct elements
System.out.println(distinctElements);
// Array Stream
System.out.println("------------------------------");
int[] numbers = {2, 3, 5, 7, 11, 13, 2,3};
System.out.println(Arrays.stream(numbers).sum()); // ==> Sum
System.out.println(Arrays.stream(numbers).count()); // ==> Count
System.out.println(Arrays.stream(numbers).distinct()); // ==> Distinct
The last line Just merely gives me reference of object, I want actual values
[A, B, C, D]
------------------------------
46
8
java.util.stream.ReferencePipeline$4#2d98a335

Answer 1

You don't see distinct values directly because IntStream.distinct() is not a terminal operation and it returns IntStream as stated in the documentation:
Returns a stream consisting of the distinct elements of this stream.
You have to terminate your stream, similarly to code you already have in your example:
List<String> distinctElements = list.stream()
.distinct()
.boxed()
.collect(Collectors.toList());
Here you call Stream.collect(Collector<? super T,A,R> collector) method which is a terminal operation and you get a list of distinct elements in return.
Both Stream.count() and IntStream.sum() are terminal operations and they perform calculation right away, closing your stream and returning a value.

Answer 2

Arrays.stream() normally returns a Stream, but it has an overloaded version: stream(int[] array), which returns an IntStream, which is a stream of primitive ints. IntStream.distinct() returns an IntStream as well.
In order to collect it, you could use collect(Collectors.toList()):
Arrays.stream(numbers)
.distinct()
.boxed()
.collect(Collectors.toList());
You could also store the result into an int[]:
Arrays.stream(numbers)
.distinct()
.toArray();