Repeating the same pattern on a regex in java?

Mel :

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.

Wiktor Stribiżew :

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