How to convert a range to a delimited string in Java 8+

Question

How can you convert a range in Java (either using java.util.stream.LongStream or java.util.stream.IntStream) to a delimited string in Java?

I have tried:

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

This prints:

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

The same can be used with IntStream. Is there a more convenient conversion of a range to a delimited string?

Answer 1

Seriously, just for the fun of it. Using guava:

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

Or

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

Or:

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

Or (seems like I got carried away a bit with this):

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();
                            })
            );

And after Holger's good points, here is even a simpler version:

    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(); 

Answer 2

With IntStream.mapToObj:

String s = IntStream.range(16, 30)
                    .mapToObj(String::valueOf)
                    .collect(Collectors.joining(","));