How to extract a substring using regex

Question

I have a string that has two single quotes in it, the ' character. In between the single quotes is the data I want.

How can I write a regex to extract "the data i want" from the following text?

mydata = "some string with 'the data i want' inside";

Answer 1

Assuming you want the part between single quotes, use this regular expression with a Matcher:

"'(.*?)'"

Example:

String mydata = "some string with 'the data i want' inside";
Pattern pattern = Pattern.compile("'(.*?)'");
Matcher matcher = pattern.matcher(mydata);
if (matcher.find())
{
    System.out.println(matcher.group(1));
}

Result:

the data i want

Answer 2

You don't need regex for this.

Add apache commons lang to your project (http://commons.apache.org/proper/commons-lang/), then use:

String dataYouWant = StringUtils.substringBetween(mydata, "'");

Answer 3

import java.util.regex.Matcher;
import java.util.regex.Pattern;

public class Test {
    public static void main(String[] args) {
        Pattern pattern = Pattern.compile(".*'([^']*)'.*");
        String mydata = "some string with 'the data i want' inside";

        Matcher matcher = pattern.matcher(mydata);
        if(matcher.matches()) {
            System.out.println(matcher.group(1));
        }

    }
}

Answer 4

Because you also ticked Scala, a solution without regex which easily deals with multiple quoted strings:

val text = "some string with 'the data i want' inside 'and even more data'"
text.split("'").zipWithIndex.filter(_._2 % 2 != 0).map(_._1)

res: Array[java.lang.String] = Array(the data i want, and even more data)

Answer 5

There's a simple one-liner for this:

String target = myData.replaceAll("[^']*(?:'(.*?)')?.*", "$1");

By making the matching group optional, this also caters for quotes not being found by returning a blank in that case.

See live demo.

Answer 6

as in javascript:

mydata.match(/'([^']+)'/)[1]

the actual regexp is: /'([^']+)'/

if you use the non greedy modifier (as per another post) it's like this:

mydata.match(/'(.*?)'/)[1]

it is cleaner.

Answer 7

String dataIWant = mydata.replaceFirst(".*'(.*?)'.*", "$1");

Answer 8

In Scala,

val ticks = "'([^']*)'".r

ticks findFirstIn mydata match {
    case Some(ticks(inside)) => println(inside)
    case _ => println("nothing")
}

for (ticks(inside) <- ticks findAllIn mydata) println(inside) // multiple matches

val Some(ticks(inside)) = ticks findFirstIn mydata // may throw exception

val ticks = ".*'([^']*)'.*".r    
val ticks(inside) = mydata // safe, shorter, only gets the first set of ticks

Answer 9

String dataIWant = mydata.split("'")[1];

See Live Demo

Answer 10

Apache Commons Lang provides a host of helper utilities for the java.lang API, most notably String manipulation methods. In your case, the start and end substrings are the same, so just call the following function.

StringUtils.substringBetween(String str, String tag)

Gets the String that is nested in between two instances of the same String.

If the start and the end substrings are different then use the following overloaded method.

StringUtils.substringBetween(String str, String open, String close)

Gets the String that is nested in between two Strings.

If you want all instances of the matching substrings, then use,

StringUtils.substringsBetween(String str, String open, String close)

Searches a String for substrings delimited by a start and end tag, returning all matching substrings in an array.

For the example in question to get all instances of the matching substring

String[] results = StringUtils.substringsBetween(mydata, "'", "'");