Is the companion object shared among all instances of the class?

Yes, a companion object in Kotlin is shared among all instances of a class. It is a kind of singleton associated with the class itself, not with any specific instance.

A companion object allows you to define functions and properties that can be called without creating an instance of the class, similar to static methods and fields in Java.

Example:

class MyClass {
    companion object {
        val sharedValue = 42
        fun printValue() {
            println("Shared value: $sharedValue")
        }
    }
}

fun main() {
    println(MyClass.sharedValue) // 42
    MyClass.printValue()        // Shared value: 42
}

Here, sharedValue and printValue are shared among all instances of MyClass.