带你读《2022技术人的百宝黑皮书》——如何避免写重复代码：善用抽象和组合（3）

Source.from(Arrays.asList("A", "B", "B", "C", "C", "C", "D"))
.statefulMap(
() -> (List<String>) new LinkedList<String>(), (buffer, element) -> {
if (buffer.size() > 0 && (!buffer.get(0).equals(element))) { return Pair.create(
new LinkedList<>(Collections.singletonList(element)), Collections.unmodifiableList(buffer));
} else { buffer.add(element);
return Pair.create(buffer, Collections.<String>emptyList());
}
},
Optional::ofNullable)
.filterNot(List::isEmpty)
.runForeach(System.out::println, system);
// prints
// [A]
// [B, B]
// [C, C, C]
// [D]

Source.from(Arrays.asList("A", "B", "B", "C", "C", "C", "D"))
.statefulMap( Optional::<String>empty, (lastElement, element) -> {
if (lastElement.isPresent() && lastElement.get().equals(element)) { return Pair.create(lastElement, Optional.<String>empty());
} else {
return Pair.create(Optional.of(element), Optional.of(element));
}
},
listOnComplete -> Optional.empty())
.via(Flow.flattenOptional())
.runForeach(System.out::println, system);
// prints
// A
// B
// C
// D