What methods can be used to extend the functionality of an already implemented class?

To extend the functionality of an already implemented class in Android (Java/Kotlin), several methods can be used:

• Inheritance — create a subclass that extends the base class and adds or overrides methods.

• Composition — include an instance of an existing class in a new class and delegate calls, adding new logic.

• Decorator — wrap an object in another object that adds functionality while preserving the interface.

• Extension Functions (in Kotlin) — add new functions to existing classes without inheritance.

Example of inheritance in Java:

public class BaseClass {
    public void doSomething() {
        System.out.println("Base implementation");
    }
}

public class ExtendedClass extends BaseClass {
    @Override
    public void doSomething() {
        super.doSomething();
        System.out.println("Extended functionality");
    }
}

Example of extension function in Kotlin:

fun String.addExclamation(): String {
    return this + "!"
}

val greeting = "Hello".addExclamation() // "Hello!"

The choice of method depends on the specific task and project constraints.