Code snippet from The Coding Café - snippet-3.java

snippet-3.java

List<Long> runningProduct = values.stream()
    .gather(Gatherers.scan(
        () -> 1L,                      // 1️⃣ Start with identity for multiplication
        (acc, val) -> acc * val        // 2️⃣ Multiply accumulated value by current
    ))
    .toList();

System.out.println("Running product: " + runningProduct);
// Output: [1, 1, 5, 15, 120, 240, 2160, 8640, 60480, 362880]
//         ↑   ↑   ↑    ↑     ↑ 
//      init 1×1 1×5  5×3  15×8  (and so on...)