Code snippet from The Coding Café - for.java

for.java

public static <T, R extends Comparable<R>> Gatherer<T, ?, T> 
        takeWhileIncreasing(Function<T, R> valueExtractor) {
    return Gatherer.of(
        () -> new Object() { R lastValue = null; },  // 1️⃣ Anonymous class for state
        (state, element, downstream) -> {
            R value = valueExtractor.apply(element);  // 2️⃣ Extract comparable value
            if (state.lastValue == null ||            // 3️⃣ First element OR
                value.compareTo(state.lastValue) > 0) {  // value is increasing
                state.lastValue = value;              // 4️⃣ Update state
                return downstream.push(element);       // 5️⃣ Pass element along
            }
            return false;  // 6️⃣ Stop gathering - sequence broken!
        }
    );
}

List<String> increasingLength = words.stream()
    .gather(takeWhileIncreasing(String::length))
    .toList();

System.out.println("Increasing length sequence: " + increasingLength);
// Output: [hello]  
// Why? "hello"(5) → "world"(5) - not increasing, so we stop!