How to implement regular expression validation in Java?

2 years ago
Olivia Parker
2 minutes

To achieve Java regular expression validation, you can utilize the regular expression classes provided by Java: java.util.regex.Pattern and java.util.regex.Matcher.

Here is a simple way to implement it:

  1. Create a Pattern object by passing the regular expression to be matched as a parameter to the Pattern.compile() method. For example, to validate if a string is a valid email address, you can use the following code:
String regex = "[a-zA-Z0-9]+@[a-zA-Z0-9]+\\.[a-zA-Z0-9]+";
Pattern pattern = Pattern.compile(regex);
  1. Instantiate a Matcher object and pass the string to be validated as a parameter to the Matcher.matches() method. For example, to validate an email address, you can use the following code:
String email = "example@example.com";
Matcher matcher = pattern.matcher(email);
boolean isValid = matcher.matches();
  1. Finally, you can use the isValid variable to determine the validation result. If isValid is true, it means the string matches the regular expression, otherwise it does not.

The complete example code is as follows:

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

public class RegexValidation {
    public static void main(String[] args) {
        String regex = "[a-zA-Z0-9]+@[a-zA-Z0-9]+\\.[a-zA-Z0-9]+";
        Pattern pattern = Pattern.compile(regex);

        String email = "example@example.com";
        Matcher matcher = pattern.matcher(email);
        boolean isValid = matcher.matches();

        System.out.println("Email is valid: " + isValid);
    }
}

Please note that the syntax of regular expressions is very flexible and powerful, and can be adjusted according to specific requirements. The email address regular expression in the example above is just a simple demonstration and may not be suitable for all cases.

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