What are access modifiers?

Access modifiers in Kotlin define the visibility of declarations (classes, interfaces, functions, properties). They control where the element can be used.

Available modifiers:

• public (default): Visible from anywhere.
• private: Visible only within the containing block (class, file).
• protected: Visible within the class and all its subclasses. Not accessible for top-level members (defined outside the class).
• internal: Visible only within the same module.

Example:

// file: Example.kt

package com.example.app

private const val PRIVATE_CONSTANT = 1 // Visible only in this file

public class PublicClass { // Visible from anywhere

    private var privateProperty = 0 // Visible only inside PublicClass

    protected open fun protectedMethod() { // Visible inside PublicClass and its subclasses
        // ...
    }

    internal fun internalMethod() { // Visible only within the module ComExampleApp
        // ...
    }
}

open class BaseClass {
    protected val protectedValue = 5 // Visible inside BaseClass and subclasses
}

class DerivedClass : BaseClass() {
    fun useProtectedValue() {
        println(protectedValue) // Access to protectedValue from subclass
    }
}