Java By Comparison

Use Collect for Terminating Complex Streams

class Inventory {

    List<Supply> supplies = new ArrayList<>();

    Map<String, Long> countDifferentKinds() {
        Map<String, Long> nameToCount = new HashMap<>();

        Consumer<String> addToNames = name -> {
            if (!nameToCount.containsKey(name)) {
                nameToCount.put(name, 0L);
            }
            nameToCount.put(name, nameToCount.get(name) + 1);
        };

        supplies.stream()
                .filter(Supply::isUncontaminated)
                .map(Supply::getName)
                .forEach(addToNames);
        return nameToCount;
    }
}

In the previous comparison ​Avoid Side Effects​, we showed you how to turn a stream into a single long value with the reduce() operator and its special case, the count() operator. We’ve also hinted at the collect() operator. This ...