Given a string
1 3 2 1 9 1 bla 3 4 3
I found that
/b[1-4]/b
will return only the digits 1 2 3 4 as this shows but String[] input = args[0].split("\b[1-4]\b"); does not return
{"1","3","2","1","1","3","4","3"}
3 Answers
I assume that you only want digits between 1 and 4. A simple split is not going to be enough. One approach could be something like this:
String str = "1 3 2 1 9 1 bla 3 4 3";
String[] splitAndFilter = Pattern.compile("\\s+")
.splitAsStream(str)
.filter(s -> s.matches("[1-4]"))
.toArray(String[]::new);
System.out.println(Arrays.toString(splitAndFilter));
1 Comment
JvdV
I guess this is nice to remove unwanted subpatterns from text like
bla-4-bla (if such thing would ever occur)The problem with your current approach is that you are trying to split on the numbers themselves. This won't give the intended result, because that on which you split gets consumed (read: removed), leaving behind everything else. Instead, try splitting on [^1-4]+:
String input = "1 3 2 1 9 1 bla 3 4 3";
String[] parts = input.split("[^1-4]+");
System.out.println(Arrays.toString(parts));
This prints:
[1, 3, 2, 1, 1, 3, 4, 3]
This will split on one or more non 1-4 characters. This happens to work for your input string, because whitespace is a delimiter, and also the non matching digits and words should be removed.
2 Comments
Tim Biegeleisen
@JvdV Good catch. I have made an edit, which should work assuming the numbers present would always be 0-9.
JvdV
That's quite a dangerous assumption but then again, nothing to proof otherwise =)
You can use just [1-4] as the regex.
import java.util.Arrays;
import java.util.regex.MatchResult;
import java.util.regex.Pattern;
class Main {
public static void main(String[] args) {
String[] matches = Pattern.compile("[1-4]")
.matcher(args[0])
.results()
.map(MatchResult::group)
.toArray(String[]::new);
System.out.println(Arrays.toString(matches));
}
}
Output:
[1, 3, 2, 1, 1, 3, 4, 3]
where the command-line argument is "1 3 2 1 9 1 bla 3 4 3"
answered Jun 17, 2020 at 17:19
Arvind Kumar Avinash
81k10 gold badges98 silver badges144 bronze badges
1 3 23 1 9 1 bla92 3 4 3produce?"\\b[1-4]\\b"[1-4]is not enough? If not, what problems can arise if I use just[1-4]?\b[1-4]\bregex to match1,2,3or4as whole words, i.e. only when they are not enclosed with other digits, letters or underscores. No idea if it is really what OP needs. One thing is sure:String#splitdoes not work the same way asMatcher#findand that is the main issue.