Repeating the same pattern on a regex in java?

Question

I have a string which may have one of two formats:

(someName,true); (where someName can be any combination of letters and numbers, and after the comma we have either true or false)
(someName,true), (anything,false), (pepe12,true); and in this case, we can have as many parenthesis groups as can be, but they are separated with a comma plus white space.

Given the following test set:

(hola,false);
comosoy12,true);
caminare)
true,comoestas

I used the following regex ^\(.*,(true|false)[)][;$] and got my expected result of true, false, false, false (quick check here). But I cannot seem to come up with the regex for the following cases:

(someName,true), (anything,false), (pepe12,true);
(hola,false);
comosoy12,true);
(batman,true), (kittycat,false);
(batman,true); (kittycat,false);

Which should return true, true, false, true, false.

s.matches("^\$\\w+,(?:true|false)\$(?:, \$\\w+,(?:true|false)\$)*;") or s.matches("^\$\\w+,(?:true|false)\$(?:,\\s+\$\\w+,(?:true|false)\$)*;") — Wiktor Stribiżew
– Wiktor Stribiżew, Commented Sep 13, 2019 at 9:05

Wiktor Stribiżew · Accepted Answer · 2019-09-13 09:18:27Z

8

You may use

^\(\w+,(?:true|false)\)(?:,\s*\(\w+,(?:true|false)\))*;$

See the regex demo. Note .* in your pattern can match any 0+ chars other than line break chars while you want to match letters and digits, thus I suggest \w (note it also matches _) or, you may use \p{Alnum} or [A-Za-z0-9].

Pattern details

^ - start of string
$\w+,(?:true|false)$ - block: (, 1+ word chars (or alhphanumeric if you use [a-zA-Z0-9] or \p{Alnum}), ,, true or false
(?:,\s*$\w+,(?:true|false)$)* - 0 or more sequences of
- , - comma
- \s* - 0+ whitespaces
- $\w+,(?:true|false)$ - block pattern
; - a ; char
$ - end of string

In Java, you may build the regex dynamically and since you want a full string match with matches, you may discard the initial ^ and final $ anchors:

String block = "\\(\\w+,(?:true|false)\\)";
String regex = block + "(?:,\\s+" + block + ")*;";
bool result = s.matches(regex);

See Java demo online:

List<String> strs = Arrays.asList("(someName,true), (anything,false), (pepe12,true);","(hola,false);","comosoy12,true);", "(batman,true), (kittycat,false);", "(batman,true); (kittycat,false);");
String block = "\\(\\w+,(?:true|false)\\)";
String regex = block + "(?:,\\s+" + block + ")*;";
Pattern p = Pattern.compile(regex);
for (String str : strs)
    System.out.println(str + " => " + p.matcher(str).matches());

Output:

(someName,true), (anything,false), (pepe12,true); => true
(hola,false); => true
comosoy12,true); => false
(batman,true), (kittycat,false); => true
(batman,true); (kittycat,false); => false

edited Sep 13, 2019 at 9:18

answered Sep 13, 2019 at 9:07

Wiktor Stribiżew

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2 Comments

Carrol Over a year ago

This one is great! What if I want to allow _ (underscore) and - (dash) on the name where I put the .*?

Wiktor Stribiżew Over a year ago

@Mel \w matches an underscore. To allow -, use [\w-]+ instead of \w+.

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