java8流的创建

绝地灬酷狼 2022-05-09 10:12 173阅读 0赞

> 流的创建有很多方式，废话不多说，看例子就懂了。

public class CreatingSteams {
        /**
         * 显示流
         *
         * @param title
         * @param stream
         * @param <T>
         */
        public static <T> void show(String title, Stream<T> stream) {
            final int SIZE = 10;
            List<T> firstElements = stream.limit(SIZE + 1)
                    .collect(Collectors.toList());
            System.out.println(title + ": ");
            for (int i = 0; i < firstElements.size(); i++) {
                if (i > 0) System.out.print(", ");
                if (i < SIZE) System.out.print(firstElements.get(i));
                else System.out.print("...");
            }
            System.out.println();
        }
    
        public static void main(String[] args) throws IOException {
            Path path = Paths.get("src/hello.txt");
            String contents = new String(Files.readAllBytes(path), StandardCharsets.UTF_8);
            //数组转化为流
            Stream<String> words = Stream.of(contents.split("\\PL+"));
            show("words", words);
            //可变长参数转化为流
            Stream<String> song = Stream.of("gently", "down", "the", "stream");
            show("song", song);
            //创建一个不包含任何参数的流
            Stream<String> silence = Stream.empty();
            show("silence", silence);
    
            //generate方法接受一个不包含任何引元的函数，创建一个无限流
            Stream<String> echos = Stream.generate(() -> "Echo");
            show("echos", echos);
    
            Stream<Double> randoms = Stream.generate(Math::random);
            show("randoms", randoms);
    
            //iterate方法接受一个种子值，以及一个函数，会反复地将该函数应用到之前的结果上。
            Stream<BigInteger> integers = Stream.iterate(BigInteger.ZERO,
                    n -> n.add(BigInteger.ONE));
            show("integers", integers);
    
            //splitAsStream按照正则分割产生一个流
            Stream<String> wordsAnotherWay = Pattern.compile("\\PL").splitAsStream(contents);
            show("wordsAnotherWay", wordsAnotherWay);
    
            try (Stream<String> lines = Files.lines(path, StandardCharsets.UTF_8)) {
                show("lines", lines);
            }
        }
    
    
    }