CODEWITHSUNDEEP
javaregex
Ammu
Ammu

Reputation: 5137

Regular Expression for matching parentheses

What is the regular expression for matching '(' in a string?

Following is the scenario :

I have a string 

str = "abc(efg)";

I want to split the string at '(' using regular expression.For that i am using 

Arrays.asList(Pattern.compile("/(").split(str))

But i am getting the following exception.

java.util.regex.PatternSyntaxException: Unclosed group near index 2
/(

Escaping '(' doesn't seems to work.

Upvotes: 95

Views: 274311

Answers (5)

Spudley
Spudley

Reputation: 168853

Two options:

Firstly, you can escape it using a backslash -- \(

Alternatively, since it's a single character, you can put it in a character class, where it doesn't need to be escaped -- [(]

Upvotes: 149

Kobi
Kobi

Reputation: 138147

  • You can escape any meta-character by using a backslash, so you can match ( with the pattern \(.
  • Many languages come with a build-in escaping function, for example, .Net's Regex.Escape or Java's Pattern.quote
  • Some flavors support \Q and \E, with literal text between them.
  • Some flavors (VIM, for example) match ( literally, and require \( for capturing groups.

See also: Regular Expression Basic Syntax Reference

Upvotes: 7

Fernando Aspiazu
Fernando Aspiazu

Reputation: 993

The solution consists in a regex pattern matching open and closing parenthesis

String str = "Your(String)";
// parameter inside split method is the pattern that matches opened and closed parenthesis, 
// that means all characters inside "[ ]" escaping parenthesis with "\\" -> "[\\(\\)]"
String[] parts = str.split("[\\(\\)]");
for (String part : parts) {
   // I print first "Your", in the second round trip "String"
   System.out.println(part);
}

Writing in Java 8's style, this can be solved in this way:

Arrays.asList("Your(String)".split("[\\(\\)]"))
    .forEach(System.out::println);

I hope it is clear.

Upvotes: 9

kurumi
kurumi

Reputation: 25609

Because ( is special in regex, you should escape it \( when matching. However, depending on what language you are using, you can easily match ( with string methods like index() or other methods that enable you to find at what position the ( is in. Sometimes, there's no need to use regex.

Upvotes: 1

StKiller
StKiller

Reputation: 7951

For any special characters you should use '\'. So, for matching parentheses - /\(/

Upvotes: 3

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