How Can I Pair Consecutive Elements from a Java Stream?

Pairing Up Stream Elements

Given a stream of elements like {0, 1, 2, 3, 4}, how can you convert it into pairs of consecutive elements (Pair objects)?

Answer:

The Java 8 stream library specializes in splitting streams into smaller parts for parallel processing, limiting its stateful pipeline stages. Therefore, directly accessing adjacent stream elements or obtaining their indexes is not possible.

To overcome this limitation, consider indexing the stream elements and accessing them from a random-access data structure like an ArrayList. For example, given an ArrayList of values:

IntStream.range(1, arrayList.size())
             .mapToObj(i -> new Pair(arrayList.get(i-1), arrayList.get(i)))
             .forEach(System.out::println);

This pipeline creates pairs of consecutive elements and runs in parallel. Note that this solution assumes the input stream is finite and not infinite.

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