// Created on savesnippets.com · https://savesnippets.com/3eclaRTWrI46Yv
class User private constructor(val id: Long, val name: String) {
    companion object {
        private var nextId = 0L
        fun create(name: String): User = User(++nextId, name)
        const val MAX_NAME_LENGTH = 50

        // Companion objects can implement interfaces too
    }
}

fun main() {
    val u = User.create("Alice")                     // calls companion factory
    println("${u.id} ${u.name}")
    println(User.MAX_NAME_LENGTH)                    // 50

    // Java callers see this as a static field:
    //   User.Companion.create("Alice")    — by default
    //   User.create("Alice")              — with @JvmStatic on the function
}