Extension Functions in Kotlin

// Extension function
fun String.removeSpaces(): String {
    return this.replace(" ", "")
}

val text = "Hello World"
println(text.removeSpaces())  // HelloWorld

// Extension properties
val String.lastChar: Char
    get() = this[length - 1]

println("Kotlin".lastChar)  // n

// Extensions on nullable types
fun String?.isNullOrEmpty(): Boolean {
    return this == null || this.isEmpty()
}

val nullString: String? = null
println(nullString.isNullOrEmpty())  // true

// Generic extensions
fun <T> List<T>.secondOrNull(): T? {
    return if (size >= 2) this[1] else null
}