创建流的方式

 1/**
 2 * many ways to create a {@link Stream} in Java api.
 3 *
 4 * @author wangy
 5 * @version 1.0
 6 * @date 2021/1/12 / 22:35
 7 */
 8public class CreateStream {
 9
10    public static <T> void show(String title, Stream<T> stream) {
11        final int SIZE = 10;
12        List<T> firstElements = stream
13                .limit(SIZE + 1)
14                .collect(Collectors.toList());
15        System.out.print(title + ": ");
16        for (int i = 0; i < firstElements.size(); i++) {
17            if (i > 0)
18                System.out.print(", ");
19            if (i < SIZE)
20                System.out.print(firstElements.get(i));
21            else
22                System.out.print("...");
23        }
24        System.out.println();
25    }
26
27    public static void main(String[] args) throws IOException {
28        Path path = Paths.get("java/resources/txt/alice30.txt");
29        String contents = new String(Files.readAllBytes(path),
30                StandardCharsets.UTF_8);
31
32        // \\PL+ 将contents按非unicode字符分割成流
33        Stream<String> words = Stream.of(contents.split("\\PL+"));
34        show("words", words);
35
36        Stream<String> song = Stream.of("gently", "down", "the", "stream");
37        show("song", song);
38
39        Stream<String> silence = Stream.empty();
40        show("silence", silence);
41
42        Stream<String> echos = Stream.generate(() -> "Echo");
43        show("echos", echos);
44
45        Stream<Double> randoms = Stream.generate(Math::random);
46        show("randoms", randoms);
47
48        Stream<BigInteger> integers = Stream.iterate(BigInteger.ONE,
49                n -> n.add(BigInteger.ONE));
50        show("integers", integers);
51
52        Stream<String> wordsAnotherWay = Pattern
53                .compile("\\PL+")
54                .splitAsStream(contents);
55        show("wordsAnotherWay", wordsAnotherWay);
56
57        try (Stream<String> lines = Files
58                .lines(path, StandardCharsets.UTF_8)) {
59            show("lines", lines);
60        }
61    }
62}