https://devops-monk.com/tags/streams/Recent content in Streams on Devops MonkHugoen-usMon, 04 May 2026 00:00:00 +0000https://devops-monk.com/tutorials/java8/streams-advanced/Mon, 04 May 2026 00:00:00 +0000https://devops-monk.com/tutorials/java8/streams-advanced/flatMap in Depth flatMap is the most powerful transformation in the Streams API. It maps each element to a stream, then flattens all those streams into one continuous stream. // Without flatMap — stream of lists Stream<List<String>> nested = Stream.of( Arrays.asList("a", "b"), Arrays.asList("c", "d"), Arrays.asList("e") ); // Stream<String>: "a", "b", "c", "d", "e" Stream<String> flat = nested.flatMap(Collection::stream); Practical flatMap Patterns Flatten orders into line items: List<LineItem> allItems = orders.stream() .flatMap(order -> order.https://devops-monk.com/tutorials/java8/java8-best-practices/Mon, 04 May 2026 00:00:00 +0000https://devops-monk.com/tutorials/java8/java8-best-practices/Streams Best Practices Do: Use streams for transformations and aggregations // Good: filter → transform → collect List<String> premiumNames = customers.stream() .filter(Customer::isPremium) .map(Customer::getName) .sorted() .collect(Collectors.toList()); // Good: aggregation Map<String, Long> countByCity = customers.stream() .collect(Collectors.groupingBy(Customer::getCity, Collectors.counting())); Don’t: Use streams for simple indexed iteration // Bad: stream for something a loop does more clearly IntStream.range(0, list.size()) .forEach(i -> System.out.println(i + ": " + list.get(i))); // Good: traditional loop wins here for (int i = 0; i < list.https://devops-monk.com/tutorials/java8/java8-overview/Mon, 04 May 2026 00:00:00 +0000https://devops-monk.com/tutorials/java8/java8-overview/Why Java 8 Matters Java 8 was released on 18 March 2014 — nearly three years after Java 7 — and it changed Java more fundamentally than any release before or since. For the first time, Java developers could write functional-style code natively, without external libraries or workarounds. The headline features — lambda expressions and the Streams API — solved a problem that had frustrated Java developers for years: the verbosity of iteration.https://devops-monk.com/tutorials/java8/streams-introduction/Mon, 04 May 2026 00:00:00 +0000https://devops-monk.com/tutorials/java8/streams-introduction/The Problem Streams Solve Consider filtering a list of orders to find the names of active premium customers who spent over $500, sorted alphabetically: // Java 7 List<String> result = new ArrayList<>(); for (Order order : orders) { if (order.isActive() && order.isPremium() && order.getTotal() > 500) { result.add(order.getCustomerName()); } } Collections.sort(result); This code is correct but reveals nothing about the structure of the computation at a glance. You have to read every line to understand what’s happening.