Array based Kotlin interview questions and answers

January 05, 2020

What is the data type of Array? val arr = arrayOf(1, 2, 3);

The type is Array<Int>.

How to Create Arrays of Different Types in Kotlin

Kotlin allows programmers to easily create different types of arrays using the arrayOf() method. Below, we’ll take a look at how to create arrays containing integer, floats, and strings using this simple but robust procedure.

val arr1 = arrayOf(1, 2, 3)
val arr2 = arrayOf(1.2, 2.3, 3.4)
val arr3 = arrayOf("Hello", "String", "Array)

How to initialize an array in Kotlin with values? How to initialize an array in Kotlin with values?
Junior

Details
In Java an array can be initialized such as:
 int numbers[] = new int[] {10, 20, 30, 40, 50}How does Kotlin's array initialization look like?
Solution
val numbers: IntArray = intArrayOf(10, 20, 30, 40, 50)

May you use IntArray and an Array<Int> is in Kotlin interchangeably? May you use IntArray and an Array<Int> is in Kotlin interchangeably?
Mid

Answer
Array<Int> is an Integer[] under the hood, while IntArray is an int[].
This means that when you put an Int in an Array<Int>, it will always be boxed (specifically, with an Integer.valueOf() call). In the case of IntArray, no boxing will occur, because it translates to a Java primitive array.
So no, we can't use them interchangeably.

What is the idiomatic way to remove duplicate strings from array? ☆☆

Details: How to remove duplicates from an Array<String?> in Kotlin?

Answer: Use the distinct extension function:

val a = arrayOf("a", "a", "b", "c", "c")
val b = a.distinct() // ["a", "b", "c"]

You can also use:

toSet, toMutableSet
toHashSet - if you don't need the original ordering to be preserved

These functions produce a Set instead of a List and should be a little bit more efficient than distinct.

May you use IntArray and an Array is in Kotlin interchangeably? ☆☆☆

Answer: Array<Int> is an Integer[] under the hood, while IntArray is an int[].

This means that when you put an Int in an Array<Int>, it will always be boxed (specifically, with an Integer.valueOf() call). In the case of IntArray, no boxing will occur, because it translates to a Java primitive array.

So no, we can't use them interchangeably.

Source: stackoverflow.com

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