java-8 - 如何在Java 8+中将范围转换为定界字符串

Question

如何将Java中的范围(使用java.util.stream.LongStream或java.util.stream.IntStream)转换为Java中的定界字符串？

我试过了:

String str = LongStream.range(16, 30)
                .boxed()
                .map(String::valueOf)
                .collect(Collectors.joining(","));
System.out.println(str);

打印:

16,17,18,19,20,21,22,23,24,25,26,27,28,29

可以与IntStream一起使用。将范围转换为带分隔符的字符串是否更方便？

Answer 1

认真地说，只是为了好玩。使用 Guava :

String result = ContiguousSet.create(
                       Range.closedOpen(16, 31), DiscreteDomain.integers())
                             .asList()
                             .toString();

或者

 String result = String.join(",",
            IntStream.rangeClosed(16, 30).mapToObj(String::valueOf).toArray(String[]::new));

或者:

String result = String.join(",",
            () -> IntStream.rangeClosed(16, 31).mapToObj(x -> (CharSequence) String.valueOf(x)).iterator());

或(似乎我对此有些迷惑):

String result = IntStream.rangeClosed(16, 31)
            .boxed()
            .collect(
                    Collector.of(
                            () -> new Object() {
                                StringBuilder sb = new StringBuilder();
                            },
                            (obj, i) -> obj.sb.append(i).append(",")
                            ,
                            (left, right) -> {
                                left.sb.append(right.sb.toString());
                                return left;
                            },
                            x -> {
                                x.sb.setLength(x.sb.length() - 1);
                                return x.sb.toString();
                            })
            );

根据Holger的观点，这是一个更简单的版本:

    StringBuilder sb = IntStream.range(16, 30)
            .collect(
                    StringBuilder::new,
                    (builder, i) -> builder.append(i).append(", "),
                    StringBuilder::append);

    if (sb.length() != 0) {
        sb.setLength(sb.length() - 2);
    }
    String result = sb.toString();