How to split() a String while maintaining whitespace

Question

How do you split a string of words and retain whitespaces?

Here is the code:

String words[] = s.split(" ");

String s contains: hello world

After the code runs, words[] contains: "hello" "" world

Ideally, it should not be an empty string in the middle, but contain both whitespaces: words[] should be: "hello" " " " " world

How do I get it to have this result?

Because I need to keep it verbatim what the user inputs. It's part of the specs. — Rock Lee, Jul 07 '15 at 15:34
`String.split` removes the delimiter you provide to it (the space in this case). If you want a different behavior, you'd have to implement a variant of `split` yourself. — Chronio, Jul 07 '15 at 15:34
@Chronio, existing api can support it. why reinvent the wheel. — Mox, Jul 07 '15 at 15:37

Reimeus · Accepted Answer · 2015-07-07T20:58:40.800

16

You could use lookahead/lookbehind assertions:

String[] words = "hello  world".split("((?<=\\s+)|(?=\\s+))");

where (?<=\\s+) and (?=\\s+) are zero-width groups.

edited Jul 07 '15 at 20:58

answered Jul 07 '15 at 15:37

Reimeus

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score 10 · Answer 2 · answered Jul 07 '15 at 15:40

10

If you can tolerate both white spaces together in one string, you can do

String[] words = s.split("\\b");

Then words contains ("hello", " ", "world").

answered Jul 07 '15 at 15:40

dcsohl

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2

+1 because in my case, this also would have been acceptable, because I was ultimately trying to reverse each word's characters, but leave the words in order and keep the same whitespace in between each word. – Rock Lee Jul 07 '15 at 20:50
OMG - this just made my entire day. Have been struggling to split words and retain spaces in between. So many workarounds that didn't work 100% - and then I see this - and everything falls into place! – slott Sep 18 '18 at 15:43
This is the best!! +1 – Eiston Dsouza May 17 '19 at 11:24

score 4 · Answer 3 · answered Jul 07 '15 at 15:39

4

s.split("((?<= )|(?= ))"); is one way.

Technically, the regular expression is using lookahead and lookbehind. The single space after each = is the delimiter.

answered Jul 07 '15 at 15:39

Bathsheba

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score 1 · Answer 4 · answered Jul 07 '15 at 15:39

You could do something like this:

List<String> result = new LinkedList<>();
int rangeStart = 0;
for (int i = 0; i < s.length(); ++i) {
  if (Character.isWhitespace(s.charAt(i))) {
    if (rangeStart < i) {
      result.add(s.substring(rangeStart, i));
    }
    result.add(Character.toString(s.charAt(i)));
    rangeStart = i + 1;
  }
}
if (rangeStart < s.length()) {
  result.add(s.substring(rangeStart));
}

Yeah, no regexes, sue me. This way you can see how it works more easily.

I tested this out, and I can attest that it works. – Rock Lee Jul 07 '15 at 20:48 — Rock Lee, Jul 07 '15 at 20:48

How to split() a String while maintaining whitespace

4 Answers4

Linked