Kotlin Substring

Substring of a string in Kotlin

To get the substring of a given string in Kotlin, you can use String.substring() function.

Call substring() function on the given String object, and specify the starting and ending indices of the substring in the string.

str.substring(startIndex, endIndex)

The following is an use case where we extract the substring of a string, given start and end indices.

h  e  l  l  o     w  o  r  l  d   <-- str
0  1  2  3  4  5  6  7  8  9  10  <-- indices
start -> 3                 9 <- end
        |<--------------->|
             substring
         l  o     w  o  r

The function returns the substring defined by the given start and end indices.

The end index is optional. So if you specify only start index, then the substring is extracted from the given start index until the end of the string.

str.substring(startIndex)

The following is an use case where we extract the substring of a string, given start index.

h  e  l  l  o     w  o  r  l  d   <-- str
0  1  2  3  4  5  6  7  8  9  10  <-- indices
start -> 3                  
        |<--------------------->|
                 substring
         l  o     w  o  r  l  d

Examples

Get substring from start index to end index

In the following program, we take a string value in str and get the substring of this string from a start index = 3 to end index = 9.

Kotlin Program

fun main() {
    val str = "hello world"
    val output = str.substring(3, 9)
    println(output)
}

Output

lo wor

Explanation

h  e  l  l  o     w  o  r  l  d   <-- str
0  1  2  3  4  5  6  7  8  9  10  <-- indices
start -> 3                 9 <- end
        |<--------------->|
             substring
         l  o     w  o  r

Get substring from start index

In the following program, we take a string value in str and get the substring of this string from a start index = 3 to end of the string.

Kotlin Program

fun main() {
    val str = "hello world"
    val output = str.substring(3)
    println(output)
}

Output

lo world

Explanation

h  e  l  l  o     w  o  r  l  d   <-- str
0  1  2  3  4  5  6  7  8  9  10  <-- indices
start -> 3                  
        |<--------------------->|
                 substring
         l  o     w  o  r  l  d