This example will demonstrate how sum unique values from two IntStreams. In the snippet below we will first concatenate two streams by calling the IntStream.concat. This will give us a stream that contains values of both streams. To find the distinct set of elements we will call the Stream.distinct. Next, we want to peform a sum reduction operation that will give us the sum of unique values from two streams or 6 (3 + 2 + 1).