How can a mechanism similar to Extension in Kotlin be implemented in Java?

Java does not have a direct equivalent of Kotlin's Extension Functions, but a similar effect can be achieved using static methods in utility classes. Such a method takes an object of the desired class as a parameter and performs additional actions.

Example:

public class StringUtils {
    public static boolean isNullOrEmpty(String s) {
        return s == null || s.isEmpty();
    }
}

// Usage
String str = "";
boolean empty = StringUtils.isNullOrEmpty(str);

Thus, it is possible to "extend" the functionality of classes without inheritance by using static methods with the object as a parameter.