Kotlin Access Modifiers

20. Kotlin Access Modifiers 20.1 Public Access Specifier 20.2 Protected Access Specifier 20.3 Private Access Specifier

There are the three access specifiers in Kotlin: Public, Protected & Private. These access specifiers can apply on both properties and methods. If no access specifiers is written then by default it will be public.

Public Access Specifier

Public properties and methods can be accessed inside and outside of the class.

Example

open class Account{
    public fun withdraw(i: Int) {
        println("Withdrawal amount is $i")
    }
}
fun main(args : Array<String>)  { 
    var acc = Account()
    acc.withdraw(10000)
}

Output

Withdrawal amount is 10000

In the above example, withdraw method is specified by public keyword that is accessed in main method.

Protected Access Specifier

Protected access specifier is generally used with inheritance. The properties and methods declared as protected can be accessed within the class and the inheriting class or child class.

Example

open class Account{
    protected val name = "Smith"
}
class Holder:Account(){
    fun name() : String
    {
        return name
    }
}
fun main(args : Array<String>)  { 
    var acc = Holder()
    var name = acc.name()
    print("Holder name is $name.")
}

Output

Holder name is Smith.

In the above example, name property is specified by the protected keyword that we can access in the inheriting class Holder.

Private Access Specifier

The private access specifier is available within the class only. This is used to hide the properties and methods to the outside of the class. A child class does not know parents private properties and methods.

Example

class Account{
    private val name = "Smith"
}
class Holder:Account(){ // error
    fun name() : String
    {
        return name
    }
}
fun main(args : Array<String>)  { 
    var acc = Holder()
    var name = acc.name()
    print("Holder name is $name.")
}

Output

Error:(4, 14) Kotlin: This type is final, so it cannot be inherited from
Error:(7, 16) Kotlin: Unresolved reference. None of the following candidates is applicable because of receiver type mismatch: 
invisible_fake final val name: String defined in Holder