Local class or classes in Java are defined in a block, which is a group of zero or more statements between balanced braces. We typically find local classes defined in the body of a method. We can define a local class in Java inside any block. In this example we will create a local class to validate email address using regex pattern or regular expression.

For example, we can define a local class in a method body, a for loop, or an if clause.

A local class in Java has access to the members of its enclosing class. In addition, a local class in Java has access to local variables. However, a local class can only access local variables that are declared final.

When a local class accesses a local variable or parameter of the enclosing block, it captures that variable or parameter.

Starting from Java SE 8, a local class can access local variables and parameters of the enclosing block that are final.

Local classes are similar to inner classes because they cannot define or declare any static members.

Local classes are non-static because they have access to instance members of the enclosing block.

We are supposed not to declare static initializers or member interfaces in a local class.

A local class can have static members provided that they are constant variables.

For example, we can validate an email address using local class by the following source code.

package com.roytuts.local.clazz;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
public class LocalClassExample {
    static String regularExpression = "^([a-zA-Z0-9])+([a-zA-Z0-9\\._-])*@([a-zA-Z0-9_-])+([a-zA-Z0-9\\._-]+)+$";
    public static void validateEmail(String email1, String email2) {
        class EmailAddress {
            Pattern pattern;
            Matcher matcher;
            EmailAddress(String email) {
                pattern = Pattern.compile(regularExpression);
                matcher = pattern.matcher(email);
            }
            public boolean validate() {
                return matcher.matches();
            }
        }
        EmailAddress emailAddress1 = new EmailAddress(email1);
        EmailAddress emailAddress2 = new EmailAddress(email2);
        if (emailAddress1.validate())
            System.out.println(email1 + " is valid.");
        else
            System.out.println(email1 + " is invalid.");
        if (emailAddress2.validate())
            System.out.println(email2 + " is valid.");
        else
            System.out.println(email2 + " is invalid.");
    }
    public static void main(String[] args) {
        validateEmail("soumitra", "[email protected]");
    }
}

By executing the above program you will get the below output:

soumitra is invalid.
[email protected] is valid.

Source Code

You can download source code.

Thanks for reading.

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