messageose.blogg.se - Arraylist kotlin

Step 3 − Add the following code to src/MainActivity. Step 2 − Add the following code to res/layout/activity_main.xml. After adding the item we are converting the mutable list to an array using the toTypedArray() function. Step 1 − Create a new project in Android Studio, go to File ? New Project and fill all required details to create a new project. Example: In the below program, mylist is the ArrayList and we added 7 items to it which are the name of weekdays. It return an Object array containing copies of the elements of the ArrayList.

Hence if you have something like : val list: List ArrayList () In this case you will not get an add () method as list is immutable. It copy the elements of the ArrayList to a new Object array. If you want to cause your list to change, you need to declare it as a MutableList.

Val p2 = arrayOf(arrayOf(Person("John", 20), Person("Mary", 15)))Īssertions.assertTrue(p1 contentDeepEquals p2) 6.This example demonstrates how to pass an arrayList to another activity using intents in Android Kotlin. For people just migrating from java, In Kotlin List is by default immutable and mutable version of Lists is called MutableList. 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. ArrayList - Kotlin Programming Language Common JVM JS Native Version 1.8 kotlin-stdlib / llections / ArrayList ArrayList Common 1.2 class ArrayList : MutableList, RandomAccess (source) JVM 1.1 typealias ArrayList ArrayList (source) JS 1.

So far, we’ve seen array comparisons for String values.