I want to split a string after a certain length.
Let's say we have a string of "message"
123456789
Split like this :
"12" "34" "567" "89"
I thought of splitting them into 2 first using
"(?<=\\G.{2})"
Regexp and then join the last two and again split into 3 but is there any way to do it on a single go using RegExp. Please help me out
Use ^(.{2})(.{2})(.{3})(.{2}).* (See it in action in regex101) to group the String to the specified length and grab the groups as separate Strings
String input = "123456789";
List<String> output = new ArrayList<>();
Pattern pattern = Pattern.compile("^(.{2})(.{2})(.{3})(.{2}).*");
Matcher matcher = pattern.matcher(input);
if (matcher.matches()) {
for (int i = 1; i <= matcher.groupCount(); i++) {
output.add(matcher.group(i));
}
}
System.out.println(output);
NOTE: Group capturing starts from 1 as the group 0 matches the whole String
And a Magnificent Sorcery from @YCF_L from comment
String pattern = "^(.{2})(.{2})(.{3})(.{2}).*";
String[] vals = "123456789".replaceAll(pattern, "$1-$2-$3-$4").split("-");
Whats the magic here is you can replace the captured group by replaceAll() method. Use $n (where n is a digit) to refer to captured subsequences. See this stackoverflow question for better explanation.
NOTE: here its assumed that no input string contains - in it.
if so, then find any other character that will not be in any of
your input strings so that it can be used as a delimiter.
test this regex in regex101 with 123456789 test string.
^(\d{2})(\d{2})(\d{3})(\d{2})$
output :
Match 1
Full match 0-9 `123456789`
Group 1. 0-2 `12`
Group 2. 2-4 `34`
Group 3. 4-7 `567`
Group 4. 7-9 `89`
