Regular Expression for matching parentheses

Question

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.

Answer 1

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 -- [(]

Answer 2

• 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

Answer 3

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.