Constructors

Kotlin allows us to define classes without any constructors. We can also define a primary constructor and one or more secondary constructors:

    class Fruit(val weight: Int) { 
        constructor(weight: Int, fresh: Boolean) : this(weight) { } 
    } 
 
    //class instantiation 
    val fruit1 = Fruit(10) 
    val fruit2 = Fruit(10, true) 

Declaring properties is not allowed for secondary constructors. If we need a property that is initialized by secondary constructors, we must declare it in the class body, and we can initialize it in the secondary constructor body. Let's define the fresh property:

    class Test(val weight: Int) { 
        var fresh: Boolean? = null 
        //define fresh property in class body 
 
        constructor(weight: Int, fresh: Boolean) : this(weight) { 
            this.fresh = fresh 
            //assign constructor parameter to fresh property 
        } 
    } 

Notice that we defined our fresh property as nullable because when an instance of the...