Java Regex: Evaluate a string against a particular pattern

Question

I have strings of a particular pattern as below which i need to validate:

String a ="test/<value>"
String b = "test/test1/<value>"
String c = "test3";
String d = "test4"

where value - can be any thing i.e alphabets,numeric,symbol,spl characters.

String c and String d are pretty straight forward.The issue comes for string a,b.

Valid Strings:

test/12 | test/abc | test/12.39 ...
test/test1/12 | test/test1/abc | test/test1/12.30
test3
test4

Invalid Strings:

test1/12
test/test123/12

test,test1,test3,test4 are key words. any change in that should return me false.

I tried with the below regex pattern:

Pattern  pattern1 = "^(test/(test1/)?[A-Za-z0-9]+|test3|test4)?/?$"

it works fine for few scenario's i.e

test/123 (pass)
test/test1/abc123(pass)

It fails when it has any symbol,decimal value or spl characters:

test/10.12 (Fail)
test/test1/@#$$ (Fail)

Pattern pattern2 = "^(test/(test1/)?[A-Za-z0-9/*!@#$%^&*()\"{}_|\\?/<>,.]+|test3|test4)?/?$";

When i use the above pattern if there are any change in the keyword it fails.

test/test1344/123(Fail)

i.e even if i change the keyword it returns as true.Expected result is false.

Please advice as to how i can validate the above strings ?

I think a tokenizer is more appropriate in your case, as it looks like you're using slash delimited tokens, and each token determines the valid values of the next one. — Tassos Bassoukos
– Tassos Bassoukos, Commented Sep 4, 2013 at 8:55
Do i understand correctly that your problem is that the second part can be anything but a variation of test1? Like, you can have test/foo, but not test/test12? — kutschkem
– kutschkem, Commented Sep 4, 2013 at 8:58

anubhava · Accepted Answer · 2013-09-04 09:10:01Z

1

You can use this regex:

^(?:test/(?:test1/)?[^/]+|test3|test4)/?$

I just replaced [A-Za-z0-9] by [^/] (any non forward slash character)

edited Sep 4, 2013 at 9:10

answered Sep 4, 2013 at 8:56

anubhava

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6 Comments

kutschkem Over a year ago

I think the problem is that he wants to also forbid things like test/test1344/123, while allowing test/test2FOOOO

Sachin Over a year ago

The keywords(test,test/test1,test3,test4) are static and what ever is after keyword can have any value.

Sachin Over a year ago

@anubhava. Thanks it works. It would be great it you can explain the expression.

anubhava Over a year ago

Most of the regex was taken from your question. I am using [^/] which means match anything except a forward slash. More importantly I removed ? just before closing /?$ from your regex otherwise regex could even match an empty string or just /. Finally I used ?: for non capturing group (not important).

kutschkem Over a year ago

Just a side note: Depending on what you want, this might not be enough, as it still allows test/test123

|

Tassos Bassoukos · Accepted Answer · 2013-09-04 08:58:30Z

0

Try ^(test3|test4|test(/test1)?/([0-9.]+|[A-Za-z]+))$/ .

answered Sep 4, 2013 at 8:58

Tassos Bassoukos

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2 Comments

Sachin Over a year ago

it fails when the value is "test/123" String test= "^(test3|test4|test(/test1)?/([0-9.]+|[A-Za-z]+))$/"; String name1="test/12"; final Pattern p = Pattern.compile(test); final boolean isValid = p.matcher(name1).matches(); have i missed something ?

Tassos Bassoukos Over a year ago

No, I wrongly added a trailing slash. Remove that and it should work. Also, try one of the many online regex building tools, such as txt2re.com

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