String validation for operators like & , !, ),(, | through regex

Question

I am totally new to reg-ex and I want to get validation for the string for valid combination of logical operators like ( ! , & , ( , ) , | ) . for Example if & | combined than it should be invalid as AND OR should come together. likewise possible invalid combination are &|, |& , (), !& ,&! etc

like example of below String

1.  (ABC)&(DFG)|!(ZXC) - pass because all operators are correctly combined
2.  !(ABC|DKJ)&VBN - pass
3.  !(ADF&(!&(BER|CTY))|DGH) = failed as !& combined
4.  !(ABC&DKJ)&|VBN - failed as & | combined

I know their several ways like I can use String's contains method to get check and reject if not passed the validation. But I am looking for solution through reg-ex in java

You may want to look into Java's `Pattern` and `Matcher` classes. The API for `Pattern` especially contains very helpful information: http://docs.oracle.com/javase/7/docs/api/java/util/regex/Pattern.html — Dragondraikk, Mar 16 '15 at 13:22
This might help: http://stackoverflow.com/questions/172303/is-there-a-regular-expression-to-detect-a-valid-regular-expression — matiasg, Mar 16 '15 at 13:25
Are you trying to solve same homework or what: http://stackoverflow.com/questions/29076008/regex-to-get-string-array-by-splitting-with-operators-with? — Pshemo, Mar 16 '15 at 13:29
And do you have to use regex here? It looks like http://www.antlr.org/ may be better tool for that. — Pshemo, Mar 16 '15 at 13:32
don't use regex for tough task..i think `|&` also an invalid combination. — Avinash Raj, Mar 16 '15 at 13:33
@LutzHorn can you please provide solution of my question using antlr — Bhargav Modi, Mar 16 '15 at 13:38

anubhava · Accepted Answer · 2015-03-16T14:14:59.483

1

Just to avoid matching invalid operator combos you can use negative lookahead regex like this:

^(?!.*?(&\\||\\|&|\\(\\)|!&|&!))

Use it with MULTILINE option like this for multiline inputs:

Pattern p = Pattern.compile( "(?m)^(?!.*?(&[!|]|[(|]&|\\(\\)))" );

RegEx Demo

For using it with a string input you can do:

boolean value = input.matches( "(?!.*?(&[!|]|[(|]&|\\(\\))).+" );

edited Mar 16 '15 at 14:14

answered Mar 16 '15 at 13:23

anubhava

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how to use it in a method sorry but please guide me as m totally new to regex – Bhargav Modi Mar 16 '15 at 13:25
1

ok check my edited answer on using `String#matches` with above regex. – anubhava Mar 16 '15 at 13:27
Although I agree with your approach, I don't think the OP should actually follow this.. Having braces will always lead to *corner cases* :) – TheLostMind Mar 16 '15 at 13:31
@anubhava thanks but sitll testing all the possible combinations as soon as all will completed I will upvote this masterpiece – Bhargav Modi Mar 16 '15 at 13:48
@anubhava it gives pass this test ideally it should not `!(ABC|DKJ)(&VBN` here )( are invalid combination – Bhargav Modi Mar 16 '15 at 13:51
Check updated regex, I had just based on your list of invalid combos in question. – anubhava Mar 16 '15 at 14:15

String validation for operators like & , !, ),(, | through regex

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