How Can Java Regex Effectively Validate Email Addresses?

Email Validation with Java Regex

Validating email addresses using regular expressions is a less recommended approach, but to proceed with this method, it's important to understand the potential issues it can present.

First, let's examine the provided regex:

b[A-Z0-9._%-] @[A-Z0-9.-] .[A-Z]{2,4}b

In Java, the following code was used:

Pattern p = Pattern.compile("\b[A-Z0-9._%-]+@[A-Z0-9.-]+\.[A-Z]{2,4}\b");
Matcher m = p.matcher("[email protected]");

However, the regex failed to match a valid email address. Let's consider the code and regex to identify potential causes for the failure.

The "find and replace" feature within Eclipse using the same regex behaved differently because it might not be using the same pattern matching algorithm or may have treated the input string differently.

To resolve this issue, you can consider using a more refined email validation regex:

public static final Pattern VALID_EMAIL_ADDRESS_REGEX = Pattern.compile("^[A-Z0-9._%+-]+@[A-Z0-9.-]+\.[A-Z]{2,6}$", Pattern.CASE_INSENSITIVE);

public static boolean validate(String emailStr) {
        Matcher matcher = VALID_EMAIL_ADDRESS_REGEX.matcher(emailStr);
        return matcher.matches();
}

This updated regex follows a stricter format to ensure valid email addresses are matched. It also uses a case-insensitive pattern to allow for variations in email casing.

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