Kotlin tutorial : String in Kotlin with examples

String in Kotlin :

What is a string :

Similar to Java, strings are a series of characters in Kotlin. String type is used for string variables. We can create one string variable similar to other. For example :

fun main(args: Array) {
    val helloWorld = "Hello World !!"
    val helloWorld2 : String = "Hello World !!"
}

Both helloWorld and helloWorld2 are string variables.

Accessing character and iterating through a string :

In Kotlin, we can access any character of a string using its index, same as Java. The index starts from 0. For example :

fun main(args: Array) {
    val helloWorld = "Hello World !!"

    print(helloWorld[0])
    print(helloWorld[4])
    print(helloWorld[6])
}

It will print :

HoW

To iterate through a string, we can use one for-loop. We can iterate a string character by character in kotlin.

fun main(args: Array) {
    val helloWorld = "Hello World !!"

    for(c in helloWorld){
        print(c)
    }
}

The above program will print the complete string. You can try println instead of print to print all characters on different lines.

Concatenate two strings :

We can concatenate two strings using the plus + operator like Java. The string is immutable in Kotlin, so it will create one new string variable on concatenation. For example :

fun main(args: Array) {
    val firstPart = "Hello"
    val secondPart = " World !!"
    var helloWorld = firstPart + secondPart;

    println(helloWorld)
}

It will print Hello World !! as the output.

Types of String literals in Kotlin:

Kotlin has two types of string literals: Escaped string and raw string. An escaped string contains one escaped character in it. For example, the below string contains tab (\t) in it.

fun main(args: Array) {
    val myString = "Hello\tWorld!!"
    println(myString)
}

Supported escaped characters in Kotlin are : \t, \b, \n, \r, \’, \”, \\ and \$.
raw string is a string defined inside a triple quote “””. It doesn’t contain any escaped character and we can even use newline characters in it. For example :

fun main(args: Array) {
    val myString = """This is the first line
        This is the second line
            This is the third line
                And fourth line
    """

    println(myString)
}

It will print the following output :

This is the first line
        This is the second line
            This is the third line
                And fourth line

To remove these spaces, we can use trimMargin() function. ‘|’ is used as margin prefix. Check the below example :

fun main(args: Array) {
    val myString = """This is the first line
        |This is the second line
            |This is the third line
                |And fourth line
    """

    println(myString.trimMargin())
}

Output :

This is the first line
This is the second line
This is the third line
And fourth line

We can also use a different character for margin prefix. For example, if ‘<‘ is a margin prefix, we can use trimMargin(“<“) to trim the whitespaces.

String templates :

In kotlin string, we can use expressions to print including the string. It is called a template expression. It should start with a dollar sign ($). Using it, we can print other values :

fun main(args: Array) {
    val count = 10

    print("value of count is $count")
}

Output :

value of count is 10

Similarly, using an expression :

fun main(args: Array) {
    val count = 10

    print("value of count is ${if (count == 10) "equal to 10" else "not equal to 10"}")
}

It will print :

value of count is equal to 10

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