listOf(1, 2, 3, 4, 5, 6) returns a read-only list of integers from 1 through 6. How do I use a list on Kotlin?Ĭreate a new List using the Kotlin standard library function listOf(), and pass in the elements of the list as arguments separated by commas. We can pass n number of parameters to a vararg variable of the defined datatype or even of a generic type. Kotlin provides us to achieve the same by defining a parameter of a function as vararg. asList(1, 2, 3), or, if we already have an array and want to pass its contents to the function, we use the spread operator (prefix the array with *): From the Kotlin Reference… When we call a vararg-function, we can pass arguments one-by-one, e.g.

Val p2 = arrayOf(arrayOf(Person('John', 20), Person('Mary', 15)))Īssertions.assertTrue(p1 contentDeepEquals p2) 6.The * operator is known as the Spread Operator in Kotlin. Moreover, we can also validate the structural equality for nested arrays holding objects of Person type using the contentDeepEquals function: data class Person (var name: String?, var age: Int?) We can solve this problem by defining the Person class as a data class: data class Person (var name: String?, var age: Int?)Īssertions.assertTrue(first contentEquals second)Īs a data class inherently defines the equals() method for value comparison, we can assert that the first and second arrays containing objects of Person type are structurally equal. That’s because we haven’t defined the equals() method in the Person class, and as a result, the contentEquals function is, by default, doing a referential equality check. Val second = arrayOf(Person('John', 20), Person('Mary', 15))įor such scenarios, the contentEquals function won’t be able to make a structural comparison of the arrays: Assertions.assertFalse(first contentEquals second)

Val first = arrayOf(Person('John', 20), Person('Mary', 15)) Let’s define a Person class and initialize two arrays that contain instances of the Person class: class Person (var name: String?, var age: Int?) Now, let’s go ahead and expand our understanding to compare arrays that contain user-defined objects. So far, we’ve seen array comparisons for String values.

Arraylist kotlin