Kotlin Variables

Kotlin has two different ways to declare variables: val (immutable variable) and var (mutable variable). The main between them is mutability.If you are planning to reassign value to variable use  var,  otherwise use val

If you try to reassign the constant variable which is val, in the Intellij IDE, you will see the following error.

When you define a variable and you assign it a value, Kotlin implicitly infers the type of it. it means you can safely remove type in here.

Lets make some example to understand better

    // Don't work
   var aVar;

   // It works
   var aVar1 : String = "hello world"

   // It works
   var number : Int? = null

   // Don't compile
   var aVar2: String?;

   // works
   val aConstant : String? = "constant Value"

    // works
   var aVariable2 = "hello Kotlin"