Kotlin is a statically typed programming language that runs on the Java Virtual Machine and can also be compiled to JavaScript source code. The Kotlin standard library provides a set of commonly used functions, which are available without any additional dependencies.
In this post, we'll take a look at some of the most commonly used functions in the Kotlin standard library and how to utilize them in your code.
Kotlin provides a set of functions for working with collections of data. These functions are available in the kotlin.collections
package.
You can create a new collection by using the arrayOf()
, listOf()
, or mutableListOf()
functions. The arrayOf()
function creates an array of the given elements, the listOf()
function creates a read-only list, and the mutableListOf()
function creates a mutable list.
For example, you can create a new array of strings like this:
val array = arrayOf("a", "b", "c")
You can create a new list of integers like this:
val list = listOf(1, 2, 3)
And you can create a new mutable list of floats like this:
val mutableList = mutableListOf(1.0f, 2.0f, 3.0f)
You can access the elements in a collection by using the get()
function. This function takes an Int
index and returns the element at that index.
For example, you can access the first element in an array like this:
val firstElement = array[0]
You can access the last element in a list like this:
val lastElement = list[list.size - 1]
And you can access the middle element in a mutable list like this:
val middleElement = mutableList[mutableList.size / 2]
You can add and remove elements from a mutable collection by using the add()
and remove()
functions. The add()
function adds an element to the end of the collection, and the remove()
function removes an element from the collection.
For example, you can add an element to a mutable list like this:
mutableList.add("d")
You can remove the first element from a mutable list like this:
mutableList.removeAt(0)
And you can remove the last element from a mutable list like this:
mutableList.removeAt(mutableList.size - 1)
Kotlin provides a set of functions for working with strings. These functions are available in the kotlin.text
package.
You can create a new string by using the String()
function. This function takes an Any
value and converts it to a string.
For example, you can create a new string from an integer like this:
val string = String(42)
You can also create a new string by concatenating two strings together. For example, you can concatenate the string "Hello" with the string "World" like this:
val string = "Hello" + "World"
You can access the characters in a string by using the get()
function. This function takes an Int
index and returns the character at that index.
For example, you can access the first character in a string like this:
val firstCharacter = string[0]
You can access the last character in a string like this:
val lastCharacter = string[string.length - 1]
And you can access the middle character in a string like this:
val middleCharacter = string[string.length / 2]
You can add and remove characters from a string by using the plus()
and minus()
functions. The plus()
function appends a character to the end of the string, and the minus()
function removes a character from the string.
For example, you can add the character "!" to the end of a string like this:
val exclamationString = string + "!"
You can remove the first character from a string like this:
val noFirstCharacterString = string.drop(1)
And you can remove the last character from a string like this:
val noLastCharacterString = string.dropLast(1)
In this post, we've taken a look at some of the most commonly used functions in the Kotlin standard library. We've seen how to create and manipulate collections, how to work with strings, and how to use some of the other commonly used functions in Kotlin.