How Can We Efficiently Generate Successive Pairs from a Stream of Elements?

Successive Pairs from a Stream

Given a stream of primitives or objects like {0, 1, 2, 3, 4}, how can we effortlessly transform it into successive pairs, as illustrated below?

{new Pair(0, 1), new Pair(1, 2), new Pair(2, 3), new Pair(3, 4)}

Delving into the Solution

While the Java 8 streams library excels at dividing streams into manageable chunks for parallel processing, it poses challenges for stateful pipeline stages. Retrieving the index of the current stream element or accessing adjacent elements are notable limitations.

To circumvent these constraints, we often employ a technique that involves leveraging indexes to drive the stream. Here's a glimpse at how we can generate pairs with this approach:

Code Snippet:

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

Expounding on the Solution:

In this example, we iterate through the ArrayList with indexes starting from 1, guaranteeing that for every index i, we can access both arrayList.get(i-1) and arrayList.get(i). The crux of the code is the mapToObj function, which converts each index into a Pair containing the adjacent elements.

Limitations and Extensions:

While this approach is effective for finite streams stored in a random-access collection, it's not applicable to infinite streams. However, the pipeline can be executed in parallel, offering performance benefits.

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