Java 8 Stream Examples

Below are list of Java Collection Stream API Usage Examples :

List<String> names = Arrays.asList("Apple", "Banana", "Mango", "Grapes", "Orange", "Apple", "PineApple", "WaterMelon", "Banana");

System.out.println(names.stream().filter( eachName -> eachName.length() > 0).collect(Collectors.toList()));

System.out.println(names.stream().filter( eachName -> eachName.length() > 0).sorted().collect(Collectors.toList()));

System.out.println(names.stream().distinct().filter( eachName -> eachName.length() > 0).collect(Collectors.toList()));

System.out.println(names.stream().filter( eachName -> eachName.length() > 0).collect(Collectors.toSet()));

System.out.println(names.stream().distinct().filter( eachName -> eachName.startsWith("A")).collect(Collectors.toSet()));

System.out.println(names.stream().distinct().filter( eachName -> eachName.startsWith("A")).skip(1).collect(Collectors.toSet()));

System.out.println(names.stream().peek(e -> e.toLowerCase()).collect(Collectors.toList()));

final AtomicInteger atomicInt = new AtomicInteger(0);

// Use Binary Func at the end to fix Duplicate key and throwing Illegal State

Map<Integer, String> mappedOut = names.stream().collect(Collectors.toMap( (eachStr) -> atomicInt.incrementAndGet(), Function.identity()));

System.out.println(mappedOut );