Recursive checking a string for repeating pattern?

Question

sorry if this is a duplicate but i couldnt find anything close.

i want to check recursively a string for the following pattern

[a-z0-9][:][a-z0-9][&][a-z0-9][:][a-z0-9]...

example

foo:bar&foo:bar1&foo:bar&foo:111&bar:2A2...

is it possible with regex and if so anyone can show me a regex expression for this?

If there is a efficient java method for this, it would be also good.

So you have to check if there are only letter and numbers in string and 1 : ? — Jure
– Jure, Commented Jul 31, 2015 at 7:33

Dzienny · Accepted Answer · 2015-07-31 09:29:18Z

2

Assuming that you want to match the whole string:

(\w+:\w+(?:&\w+:\w+)*)

See a demo.

Regular expression visualization

Debuggex Demo

edited Jul 31, 2015 at 9:29

answered Jul 31, 2015 at 7:38

Dzienny

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6 Comments

Gobliins Over a year ago

does "(..)+" means repeating?

Dzienny Over a year ago

+ means match one or more times ? means match zero or one time.

Dzienny Over a year ago

@AvinashRaj It depends on what exactly is supposed to be matched, but you may be right. I updated the answer.

nhahtdh Over a year ago

You should always use the second version. The first version, if used with String.matches in Java, which asserts that the whole string has to match the regex, will match foo:barfoo:bar1 regex101.com/r/fN7uX4/1

nhahtdh Over a year ago

Another thing is that \w also matches capital letters and _, which is not in the original expression.

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Avinash Raj · Accepted Answer · 2015-07-31 07:36:20Z

2

Just put the pattern inside a group with a preceding & and then make it to repeat zero or more times.

^[a-z0-9]+:[a-z0-9]+(?:&[a-z0-9]+:[a-z0-9]+)*$

Anchors won't be needed if you use matches method.

DEMO

answered Jul 31, 2015 at 7:36

Avinash Raj

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Comments

Akash Thakare · Accepted Answer · 2015-07-31 07:36:54Z

1

If you want to match value:value& as a sole element multiple times,

(([a-z0-9]+:)([a-z0-9]+&))+

NOTE : It won't match value:value&value:,value&value&value: etc.

answered Jul 31, 2015 at 7:36

Akash Thakare

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