Java 8 Stream进行实战总结及原理应用

小结本文探究了Stream的实现原理，介绍了怎么用Java 8 Stream的开源框架 StreamEx来解答StackOverflow上一些经常被问到关于Java 8 Stream的问题：

• Convert Java 8 List<V> into Map<K, V>

用JDK Stream API:

Map<String, Choice> result =    choices.stream().collect(Collectors.toMap(Choice::getName,                                              Function.identity()));

用StreamEx API：

Map<String, Choice> result = StreamEx.of(choices).toMap(Choice::getName);

• Custom thread pool in Java 8 parallel stream

用JDK Stream API:

ForkJoinPool forkJoinPool = new ForkJoinPool(2);forkJoinPool.submit(() ->    //parallel task here, for example    IntStream.range(1, 1_000_000).parallel().filter(PrimesPrint::isPrime).collect(toList())).get();

用StreamEx API：

IntStreamEx.range(1<b>本文来源gao@!dai!ma.com搞$$代^@码!网</b>, 1_000_000).parallel(new ForkJoinPool(2))           .filter(PrimesPrint::isPrime).toList();

• Java 8 Distinct by property

用JDK Stream API:

public static <T> Predicate<T> distinctByKey(Function<? super T, ?> keyExtractor) {    Set<Object> seen = ConcurrentHashMap.newKeySet();    return t -> seen.add(keyExtractor.apply(t));}persons.stream().filter(distinctByKey(Person::getName));

用StreamEx API：

StreamEx.of(persons).distinctBy(Person::getName);

• Is it possible to cast a Stream in Java 8?

用JDK Stream API:

Stream.of(objects)    .filter(Client.class::isInstance)    .map(Client.class::cast)    .map(Client::getID)    .forEach(System.out::println);

用StreamEx API：

StreamEx.of(objects)    .select(Client.class)    .map(Client::getID)    .forEach(System.out::println);

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