正则表达式匹配特定模式

Question

Definitely not an expert at Regex so I'm struggling here a bit. I'd like to create a pattern that will match the following format:

cat:hairy, rat:hairless               [correct]

cat:hairy, rat:hairless, dog:fat      [correct]

cat:hairy,      rat:hairless          [correct]



cat                                   [incorrect]

cat, dog                              [incorrect]

cat:hairy,                            [incorrect]

cat:hairy, monkey, dog:fat            [incorrect]

cat:hairy rat:hairless, dog:fat       [incorrect]

So far the regex I have is as follows:

((\S):(\S))

However, this does not work in all cases. Any help would be appreciated!

Update Language : Java Format : the xxx:yyy can be any letter or number, upper or lower case

Answer 1

You may use the following regex:

^[a-zA-Z0-9]+:[a-zA-Z0-9]+(?:,\s+[a-zA-Z0-9]+:[a-zA-Z0-9]+)+$

See the regex demo

Details :

• ^ - start of string
• [a-zA-Z0-9]+ - 1 or more alphanumerical chars
• : - a colon
• [a-zA-Z0-9]+ - 1 or more alphanumerical chars
• (?:,\\s+[a-zA-Z0-9]+:[a-zA-Z0-9]+)+ - 1 or more sequences of
  • , - comma
  • \\s+ - 1 or more whitespaces
  • [a-zA-Z0-9]+ - 1 or more alphanumerical chars
  • : - a colon
  • [a-zA-Z0-9]+ - 1 or more alphanumerical chars
• $ - end of string

Depending on the regex flavor and purpose, [a-zA-Z0-9] may be replaced with [[:alnum:]] (POSIX, Ruby, PCRE) or \\p{Alnum} (Java). So, in Java, you'd use

.matches("\\p{Alnum}+:\\p{Alnum}+(?:,\\s+\\p{Alnum}+:\\p{Alnum}+)+")

Note there is no need for ^ and $ as .matches() anchors the pattern by default.

Answer 2

There is one scenario that is not listed as correct or incorrect, but implied correct by your first regex ((\\S):(\\S)) : a singleton cat:hairy . In this case, then Wiktor's excellent solution would be terminated with *$ instead of +$ .