Extracting email addresses from a string using Java regular expressions

01 Oct 2023

regex

In this blog post, we will explore how to extract email addresses from a string in Java using regular expressions. Regular expressions are powerful patterns that can be used to match and extract specific patterns from textual data.

The regular expression pattern

To extract email addresses from a string, we can use the following regular expression pattern:

String pattern = "\\b[A-Za-z0-9._%+-]+@[A-Za-z0-9.-]+\\.[A-Za-z]{2,}\\b";

Let’s break down the pattern:

\\b: Matches word boundaries, ensuring that the email address is not part of a larger word.
[A-Za-z0-9._%+-]+: Matches one or more letters, digits, periods, underscores, percentage signs, or plus/minus signs. These are valid characters for the local part of an email address.
@: Matches the @ symbol.
[A-Za-z0-9.-]+: Matches one or more letters, digits, periods, or hyphens. These are valid characters for the domain name part of an email address.
\\.: Matches a period (escaped with a backslash).
[A-Za-z]{2,}: Matches two or more letters. This is the top-level domain of the email address.

Using the regular expression in Java

To extract email addresses from a string in Java, we can use the java.util.regex.Pattern and java.util.regex.Matcher classes:

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

public class EmailExtractor {
    public static void main(String[] args) {
        String input = "Lorem ipsum dolor sit amet, consectetur adipiscing elit. " +
                       "Email addresses: info@example.com, john.doe@example.com";
        String pattern = "\\b[A-Za-z0-9._%+-]+@[A-Za-z0-9.-]+\\.[A-Za-z]{2,}\\b";

        Pattern regexPattern = Pattern.compile(pattern);
        Matcher matcher = regexPattern.matcher(input);

        while (matcher.find()) {
            String email = matcher.group();
            System.out.println(email);
        }
    }
}

In this example, we define a sample input string that contains two email addresses. We compile the regular expression pattern into a Pattern object using Pattern.compile(). We then create a Matcher object using matcher(), passing in the input string.

We use the find() method of the Matcher object to find matches in the input string. For each match, we retrieve the email address using group() and print it.

Conclusion

Regular expressions provide a powerful way to extract email addresses from a string in Java. By using the regular expression pattern we discussed and the Pattern and Matcher classes provided by Java, extracting email addresses becomes a relatively simple task.

#java #regex