本文列舉了十個使用一行程式碼即可獨立完成(不依賴其他程式碼)的業務邏輯，主要依賴的是Java8中的Lambda和Stream等新特性以及try-with-resources、JAXB等。

對列表/陣列中的每個元素都乘以2

// Range是半開區間
int[] ia = range(1, 10).map(i -> i * 2).toArray();
List<Integer> result = range(1, 10).map(i -> i * 2).boxed().collect(toList());

計算集合/陣列中的數字之和

range(1, 1000).sum
 
();
range(1, 1000).reduce(0, Integer::sum);
Stream.iterate(0, i -> i + 1).limit(1000).reduce(0, Integer::sum);
IntStream.iterate(0, i -> i + 1).limit(1000).reduce(0, Integer::sum);

驗證字串是否包含集合中的某一字串

final List<String> keywords = Arrays.asList("brown", "fox", "dog", "pangram");
final String tweet = "The quick brown fox jumps over a lazy dog. #pangram http://www.rinkworks.com/words/pangrams.shtml"
 
;

keywords.stream().anyMatch(tweet::contains);
keywords.stream().reduce(false, (b, keyword) -> b || tweet.contains(keyword), (l, r) -> l || r);

讀取檔案內容

try (BufferedReader reader = new BufferedReader(new FileReader("data.txt"))) {
  String fileText = reader.lines().reduce("", String::concat);
}

try
 
 (BufferedReader reader = new BufferedReader(new FileReader("data.txt"))) {
  List<String> fileLines = reader.lines().collect(toCollection(LinkedList<String>::new));
}

try (Stream<String> lines = Files.lines(new File("data.txt").toPath(), Charset.defaultCharset())) {
  List<String> fileLines = lines.collect(toCollection(LinkedList<String>::new));
}

輸出歌曲《Happy Birthday to You!》 – 根據集合中不同的元素輸出不同的字串

range(1, 5).boxed().map(i -> { out.print("Happy Birthday "); if (i == 3) return "dear NAME"; else return "to You"; }).forEach(out::println);

過濾並分組集合中的數字

Map<String, List<Integer>> result = Stream.of(49, 58, 76, 82, 88, 90).collect(groupingBy(forPredicate(i -> i > 60, "passed", "failed")));

分組統計

Map<String, Long> counting = items.stream().collect(Collectors.groupingBy(Function.identity(), Collectors.counting()));

獲取並解析xml協議的Web Service

FeedType feed = JAXB.unmarshal(new URL("http://search.twitter.com/search.atom?&q=java8"), FeedType.class);
JAXB.marshal(feed, System.out);

獲得集合中最小/最大的數字

int min = Stream.of(14, 35, -7, 46, 98).reduce(Integer::min).get();
min = Stream.of(14, 35, -7, 46, 98).min(Integer::compare).get();
min = Stream.of(14, 35, -7, 46, 98).mapToInt(Integer::new).min();

int max = Stream.of(14, 35, -7, 46, 98).reduce(Integer::max).get();
max = Stream.of(14, 35, -7, 46, 98).max(Integer::compare).get();
max = Stream.of(14, 35, -7, 46, 98).mapToInt(Integer::new).max();

並行處理

long result = dataList.parallelStream().mapToInt(line -> processItem(line)).sum();

集合上的各種查詢(LINQ in Java)

List<Album> albums = Arrays.asList(unapologetic, tailgates, red);

//篩選出至少有一個track評級4分以上的專輯，並按照名稱排序後打印出來。
albums.stream()
  .filter(a -> a.tracks.stream().anyMatch(t -> (t.rating >= 4)))
  .sorted(comparing(album -> album.name))
  .forEach(album -> System.out.println(album.name));

//合併所有專輯的track
List<Track> allTracks = albums.stream()
  .flatMap(album -> album.tracks.stream())
  .collect(toList());

//根據track的評分對所有track分組
Map<Integer, List<Track>> tracksByRating = allTracks.stream()
  .collect(groupingBy(Track::getRating));