Kotlin charsequence vs string

Kotlin java create string from charsequence code example

Example: Using arrayOf() Kotlin library provides a function to create an array of different types of Strings. We can also use emptyArray() to create an empty array of Strings in Kotlin.

What’s the Kotlin equivalent of Java’s String[]?

String is a collection which is implemented using String class . As per the Kotlin documentation, a string can be defined as follows −

Class String : Comparable, CharSequence

In Kotlin, a string is a collection of characters. Strings are immutable in nature which means they are read-only. The length and elements of a string can be modified once declared.

In Java, we have an option to create an empty String array by defining it like String[] . In this article, we will see how we can achieve the same using Kotlin library function.

Example: Using arrayOf()

Kotlin library provides a function to create an array of different types of Strings. In this example, we will create an array of Strings using arrayOf() .

Example

fun main(args: Array) < var myEmptyStringArray = arrayOf() println(myEmptyStringArray) >

Output

It will generate the following output −

In the above piece of code, we have declared an empty array of Strings and named it as «myEmptyStringArray» and we have printed its contents. It generates the hash code of the memory location.

Example: Using arrayOfNulls()

arrayOfNulls() is another function which creates an array of empty Strings. In the following example, we will modify our previous example and we will create an array of empty Strings.

Example

fun main(args: Array) < var myEmptyStringArray: Array= arrayOfNulls(3) println(myEmptyStringArray) >

Output

It will generate the following output −

In the above piece of code, we have declared an empty array of Strings and named it as «myEmptyStringArray» and we have printed its contents. It generates the hash code of the memory location.

Example: Using emptyArray()

We can also use emptyArray() to create an empty array of Strings in Kotlin. In the following example, we will create an empty array of Strings using emptyArray() .

Example

fun main(args: Array) < var myEmptyStringArray: Array= emptyArray() println(myEmptyStringArray) >

Output

It will generate the following output −

How is String class in Kotlin Standard library implemented?

Kotlin’s standard library is shared between all the platforms supported by Kotlin, so it contains only signatures of methods. Several classes are implemented identically to platform-specific ones: for example, in Kotlin/JVM kotlin.text.StringBuilder is implemented as a type-alias to java.lang.StringBuilder .

However, some types are mapped by the compiler specifically to platform types (some methods are removed, some methods are renamed). These types include primitive types (Int, Byte, etc.), String and collections.

As for JVM the rough mapping is:

kotlin.String.length => java.lang.String.length() kotlin.String.compareTo(other: String) => java.lang.String.compareTo(java.langString anotherString) kotlin.String.get(index: Int) => java.lang.String.charAt(int index) kotlin.String.plus(other: Any?) is implemented as plain Java concatentation (it is implemented on compiler level with StringConcatFactory magic) kotlin.String.subSequence(startIndex: Int, endIndex: Int) => java.lang.String.subSequence(int beginIndex, int endIndex) 

Other java.lang.String methods like intern are not available in kotlin.String (however, it is actually possible to reference java.lang.String directly).

In Kotlin/Native kotlin.String is implemented with C++: https://github.com/JetBrains/kotlin-native/blob/045b20a36b8a1fe86716a99cb25f03021e583592/runtime/src/main/cpp/KString.cpp.

JavaScript implementation involves builtin JavaScript String too.

Java — How to convert a String to CharSequence?, CharSequence is an interface and String is its one of the implementations other than StringBuilder, StringBuffer and many other. So, just as you use InterfaceName i = new ItsImplementation (), you can use CharSequence cs = new String («string») or simply CharSequence cs = «string»; Share answered Jan …

How can I use a Java String method (split) directly from Kotlin source?

You can cast a kotlin.String to a java.lang.String then use the java.lang.String#split since kotlin.String will be mapped to java.lang.String , but you’ll get a warnings. for example:

// v--- PLATFORM_CLASS_MAPPED_TO_KOTLIN warnings val parts: Array = (line as java.lang.String).split("\t") 

You also can use the java.util.regex.Pattern#split instead, as @Renato metioned it will slower than java.lang.String#split in some situations. for example:

val parts: Array = Pattern.compile("\t").split(line, 0) 

But be careful, kotlin.String#split ‘s behavior is different with java.lang.String#split , for example:

val line: String = "example\tline\t" // v--- ["example", "line"] val parts1: Array = Pattern.compile("\t").split(line, 0) // v--- ["example", "line", ""] val parts2 = line.split("\t".toRegex()) 

(line as java.lang.String).split(delimiter) 

But it’s not recommended to not use the kotlin.String as the compiler might tell you.

Kotlin String — GeeksforGeeks, To create an empty string in Kotlin, we need to create an instance of String class. var variable_name = String () String elements and templates – String Element – The character, digit or any other symbol present in string is called as element of a String. We can easily access the element of the string using string …

Kotlin Regular Expression

Regular Expressions are a fundamental part of almost every programming language and Kotlin is no exception to it. In Kotlin, the support for regular expression is provided through Regex class. An object of this class represents a regular expression, that can be used for string matching purposes.

We can easily find use of regular expressions in different kind of software, from simplest to incredibly complex applications.
Before preceding this article have a look at Regular Expression in Java

Constructors –

1. (pattern: String) : This constructor creates a regular expression based on the pattern string.
2. (pattern: String, option: RegexOption) : This constructor creates a regular expression based on the specified pattern and the option. The option is a constant of RegexOption enum class.
3. (pattern: String, options: Set) : This constructor creates a regular expression on the basis of the specified string pattern and the set of options specified in the set.

Properties –

1. val options: Set : It contains the set of options which are to be used at the time of regex creation.
2. val pattern: String : It contains the string describing the pattern.

fun containsMatchIn(input: CharSequence): Boolean

fun compareTo(other: String): Int

fun equals(other: Any?): Boolean

operator fun plus(other: Any?): String

fun subSequence(startIndex: Int, endIndex: Int): CharSequence