It is used to add all the elements in the specified collection to current collection. Open fun addAll(elements: Collection): Boolean It is used to insert an element at specific index. It is used to add the specific element into the collection.

It is used to create an ArrayList filled from the elements of collection. It is used to create an ArrayList of specified capacity. Constructor of Kotlin ArrayList Constructor The elements of ArrayList class are accessed randomly as it works on index basis. ArrayList class is non synchronized and it may contains duplicate elements. Kotlin ArrayList class follows the sequence of insertion order. ArrayList class provides both read and write functionalities. Which means the size of ArrayList class can be increased or decreased according to requirement. So, it explains how the reassignment happens.įurther, let’s look at the implementation of List‘s ‘ +‘ ( plus operation) operator: public operator fun Collection.Kotlin ArrayList class is used to create a dynamic array. Now, let’s take a closer look at this compilation error. First, as the List interface and its super types don’t have the plusAssign() function, here, myList += “Tom Cruise” is the same as myList = myList + “Tom Cruise”. However, the error message is different this time: “ Kotlin: Val cannot be reassigned.” Next, let’s test the += operator: val myList = listOf('Tom Hanks', 'Brad Pitt')Īs we’ve expected, the code doesn’t compile either. If we compile the code above, the compiler complains: “Kotlin: Unresolved reference: add.” This is expected, as the List interface doesn’t have the add() method. But let’s create a test to verify if it’s true: var myList = listOf('Tom Hanks', 'Brad Pitt')

Since List is read-only, we can’t add an element to it. Finally, let’s look at the List type in Kotlin.

Arraylist in kotlin