What can replace inheritance and what are the alternative methods?

1. Object Composition: Instead of inheritance, where one class inherits properties and behavior from another, an object can contain an instance of another object and use its functionality (Delegation pattern).

2. Interfaces: A class can implement one or more interfaces, thereby committing to provide certain behavior. This allows achieving polymorphism without a strict inheritance hierarchy.

3. Extension Functions in Kotlin: Allow adding new functions to existing classes without modifying their source code, simulating the addition of behavior.

4. Traits (a concept from other languages, in Kotlin can be implemented via interfaces with default methods): A set of methods that can be used by classes through "mixing". Interfaces with default method implementations in Kotlin partially realize this concept.

Example of composition:

class Engine {
    fun start() {
        // Engine start logic
    }
}

class Car {
    private val engine = Engine() // Composition

    fun drive() {
        engine.start()
        // Car driving logic
    }
}

Example of an interface:

interface Drawable {
    fun draw()
}

class Circle : Drawable {
    override fun draw() {
        // Circle drawing logic
    }
}

class Square : Drawable {
    override fun draw() {
        // Square drawing logic
    }
}

Example of an extension function:

fun String.removeVowels(): String {
    return this.replace("[aeiouAEIOU]".toRegex(), "")
}

fun main() {
    val text = "Hello World"
    println(text.removeVowels()) // Output: Hll Wrld
}