Regex doesnt stop after sign

December 10, 2021

Hi I have regex like this

(.*(?=\sI+)*) (.*)

But it doesn’t capture groups correctly as I need.

For this example data :

Vladimir Goth
Langraab II Landgraab
Léa Magdalena III Rouault Something
Anna Maria Teodora
Léa Maria Teodora II

1,2 are only correctly captured.

So what I need is

If there is no I+ is split by first space.
If after I+ there are other words first gorup should contains all to I+. So, group1 for 3rd example should be Léa Magdalena III
If after I+ there aren’t any other words like in example 5, group1 should be capture to first space.

@Edit
I+ should be replaced by roman numbers

>Solution :

If you want to support any Roman numbers you can use

^(\S+(?:.*\b(?=[MDCLXVI])M{0,4}(?:CM|CD|D?C{0,3})(?:XC|XL|L?X{0,3})(?:IX|IV|V?I{0,3})\b(?= +\S))?) +(.*)

If you need to support Roman numbers up to XX (exclusive):

^(\S+(?:.*\b(?=[XVI])X?(?:IX|IV|V?I{0,3})\b(?= +\S))?) +(.*)

See the regex demo #1 and demo #2. Replace spaces with \h or \s in the Java code and double backslashes in the Java string literal.

Details:

^ – start of string
( – Group 1 start:
- \S+ – one or more non-whitespaces
- (?: – a non-capturing group:
  - .* – any zero or more chars other than line break chars as many as possible
  - \b – a word boundary
  - (?=[MDCLXVI]) – require at least one Roman digit immediately to the right
  - M{0,4}(?:CM|CD|D?C{0,3})(?:XC|XL|L?X{0,3})(?:IX|IV|V?I{0,3}) – a Roman number pattern
  - \b – a word boundary
  - (?= +\S) – a positive lookahead that requires one or more spaces and then one non-whitespace right after the current position
- )? – end of the non-capturing group, repeat one or zero times (it is optional)
) – end of the first group
+ – one or more spaces
(.*) – Group 2: the rest of the line.

In Java:

String regex = "^(\\S+(?:.*\\b(?=[MDCLXVI])M{0,4}(?:CM|CD|D?C{0,3})(?:XC|XL|L?X{0,3})(?:IX|IV|V?I{0,3})\\b(?=\\h+\\S))?)\\h+(.*)";
// Or
String regex = "^(\\S+(?:.*\\b(?=[XVI])X?(?:IX|IV|V?I{0,3})\\b(?=\\s+\S))?)\\s+(.*)";