Java技術棧
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之前棧長分享過 Java 8 一系列新特性的文章，其中重點介紹了 Stream。
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今天來分享下在 Java 8 中建立 Stream 的 10 種方式，我就整理了 10 種，其實還有更多，僅供大家參考學習下。
1、Stream.of 可變參數
Stream<String> stream1 = Stream.of("A", "B", "C");System.out.println("stream1:" + stream1.collect(joining()));of("A", "B", "C");System.out.println("stream1:" + stream1.collect(joining())); 程式輸出：
stream1:ABC
2、Stream.of 數組
String[] values = new String[]{"A", "B", "C"};Stream<String> stream2 = Stream.of(values);System.out.println("stream2:" + stream2.collect(joining()));new String[]{"A", "B", "C"};Stream<String> stream2 = Stream.of(values);System.out.println("stream2:" + stream2.collect(joining())); stream2:ABC
看 Stream.of 源碼，上面這兩種方式其實就是第三種方式的包裝版。
public static<T> Stream<T> of(T... values) { return Arrays.stream(values);} return Arrays.stream(values);} 我們直接使用源碼中的方式也是一樣的。
3、Arrays.stream
String[] values = new String[]{"A", "B", "C"};Stream<String> stream3 = Arrays.stream(values);System.out.println("stream3:" + stream3.collect(joining()));new String[]{"A", "B", "C"};Stream<String> stream3 = Arrays.stream(values);System.out.println("stream3:" + stream3.collect(joining())); stream3:ABC
4、List
List<String> list = Arrays.asList("A", "B", "C");Stream<String> stream4 = list.stream();System.out.println("stream4:" + stream4.collect(joining()));list = Arrays.asList("A", "B", "C");Stream<String> stream4 = list.stream();System.out.println("stream4:" + stream4.collect(joining())); stream4:ABC
5、Set
Set<String> set = new HashSet<>(Arrays.asList("A", "B", "C"));Stream<String> stream5 = set.stream();System.out.println("stream5:" + stream5.collect(joining()));String> set = new HashSet<>(Arrays.asList("A", "B", "C"));Stream<String> stream5 = set.stream();System.out.println("stream5:" + stream5.collect(joining())); stream5:ABC
6、Map
Map<String, String> map = new HashMap<>();map.put("1", "A");map.put("2", "B");map.put("3", "C");Stream<String> stream6 = map.values().stream();System.out.println("stream6:" + stream6.collect(joining()));new HashMap<>();map.put("1", "A");map.put("2", "B");map.put("3", "C");Stream<String> stream6 = map.values().stream();System.out.println("stream6:" + stream6.collect(joining())); stream6:ABC
7、Stream.iterate
Stream<String> stream7 = Stream.iterate("A", e -> String.valueOf((char) (e.charAt(0) + 1))).limit(3);System.out.println("stream7:" + stream7.collect(joining()));"A", e -> String.valueOf((char) (e.charAt(0) + 1))).limit(3);System.out.println("stream7:" + stream7.collect(joining())); stream7:ABC
8、Pattern
String value = "A B C";Stream<String> stream8 = Pattern.compile("\\W").splitAsStream(value);System.out.println("stream8:" + stream8.collect(joining()));"A B C";Stream<String> stream8 = Pattern.compile("\\W").splitAsStream(value);System.out.println("stream8:" + stream8.collect(joining())); stream8:ABC
9、Files.lines
try { Stream<String> stream9 = Files.lines(Paths.get("d:/data.txt")); System.out.println("stream9:" + stream9.collect(joining()));} catch (IOException e) { e.printStackTrace();} Stream<String> stream9 = Files.lines(Paths.get("d:/data.txt")); System.out.println("stream9:" + stream9.collect(joining()));} catch (IOException e) { e.printStackTrace();} data.txt檔案内容如下：
ABCBC stream9:ABC
10、Stream.generate
Stream<String> stream10 = Stream.generate(() -> "A").limit(3);System.out.println("stream10:" + stream10.collect(joining()));"A").limit(3);System.out.println("stream10:" + stream10.collect(joining())); stream10:AAA
好了，這是棧長整理的 10 種建立 Stream 的方式，是不是很騷？如果你還知道其他的騷操作，可以留言告訴大家，讓大家記住你的頭像和ID。