Java regex to find +(plus sign) with characters

Question

With java regex i want to find the word "C++" and it should not be positive with only "C".

The below code should explain the rest, see here

import java.util.*; import java.util.regex.*; public class MyClass { public static void main(String args[]) { String test = "Framework, c++ and Visual Studio IDEs."; Pattern p = Pattern.compile("(?i).*\\bc\\+\\+\\b.*"); Matcher m = p.matcher(test); if(m.find()) { System.out.println("Pattern1 True"); } p = Pattern.compile("(?i).*\\Bc.+.+\\B.*"); m = p.matcher(test); if(m.find()) { System.out.print("Pattern2 True"); } p = Pattern.compile("(?i).*\\bc+$\\b.*"); m = p.matcher(test); if(m.find()) { System.out.println("Pattern3 is True but how to return false"); } p = Pattern.compile("(?i).*\\Bc\\B.*"); m = p.matcher(test); if(m.find()) { System.out.println("Pattern4 is True"); } if(test.toLowerCase() .contains("c++")) { System.out.print("Contains c++ True"); } if(test.toLowerCase().contains("C")) { System.out.print("Contains C True"); } } }

Use a non-word boundary, Pattern p = Pattern.compile("(?i).*\\bc\\+\\+\\B.*"); — Wiktor Stribiżew
– Wiktor Stribiżew, Commented Nov 16, 2022 at 20:50
@WiktorStribiżew nice one with C++, will this work with only "C" — Pradyut Bhattacharya
– Pradyut Bhattacharya, Commented Nov 16, 2022 at 20:56
If you want to match C not followed with ++, use \bC\b(?!\+\+) — Wiktor Stribiżew
– Wiktor Stribiżew, Commented Nov 16, 2022 at 21:07

Wiktor Stribiżew · Accepted Answer · 2022-11-16 22:14:41Z

1

You can use

Pattern p = Pattern.compile("(?i).*\\bc\\+\\+\\B.*"); // C++ Pattern p = Pattern.compile("(?i).*\\bC\\b(?!\\+{2}).*"); // C only

Here,

\b - a word boundary
c\+\+ - a c++ string
\B - a non-word boundary, on the right, there must be end of string or a non-word char
(?!\+{2}) - a negative lookahead that fails the match if there is a ++ string immediately to the right of the current location.

answered Nov 16, 2022 at 22:14

Wiktor Stribiżew

631k41 gold badges502 silver badges632 bronze badges

Sign up to request clarification or add additional context in comments.

2 Comments

Pradyut Bhattacharya Over a year ago

for omitting all appending characters with C - "(?i).*\\bC\\b(?!\\+|#|\\$|\*|\\^|%|&).*" Phew is there is anyway to do a asterisk with those omitting characters, can we propose the regex community to do so?

Wiktor Stribiżew Over a year ago

@PradyutBhattacharya You need to make sure what your "word" boundary is like. If you can describe it using a finite amount of special chars, then the above pattern is a solution. If you can describe it in any other way, please do and we'll be able to adjust the pattern.

E-Riz · Accepted Answer · 2022-11-16 20:56:36Z

This seems to work at detecting either "C++" or "c++" anywhere in an input string.

String regex = ".*[cC]\\+\\+.*"; java.util.regex.Pattern.matches(regex, "This is NOT c++ !");

Results in true, but

java.util.regex.Pattern.matches(regex, "This is NOT c!");

results in false.

Pradyut Bhattacharya · Accepted Answer · 2022-11-17 11:01:18Z

tough time omitting characters for only C

p = Pattern.compile("(?i).*\\bC\\b(?!\\+|#|\\$|\\*|\\^|%|&|\\.).*"); m = p.matcher(test); if(m.find()) { System.out.println("C is true"); } p = Pattern.compile("(?i).*\\bc\\+\\+\\B.*"); m = p.matcher(test); if(m.find()) { System.out.println("C++ is true"); } p = Pattern.compile("(?i).*\\bc\\#\\B.*"); m = p.matcher(test); if(m.find()) { System.out.println("C# is true"); }

Collectives™ on Stack Overflow

Java regex to find +(plus sign) with characters

3 Answers 3

2 Comments

1 Comment

Comments

Hot Network Questions

Collectives™ on Stack Overflow

3 Answers 3

2 Comments

1 Comment

Comments

Related