Kotlin String dropWhile()

Kotlin String dropWhile() Tutorial

The String.dropWhile() function in Kotlin is used to create a substring by excluding characters from the beginning of the original string based on a given predicate condition. It returns a new string that consists of the remaining characters after dropping the prefix that matches the specified condition.

In this tutorial, we’ll explore the syntax of the dropWhile() function and provide examples of its usage in Kotlin strings.

Syntax

The syntax of the dropWhile() function is as follows:

fun String.dropWhile(
    predicate: (Char) -> Boolean
): String

where

Parameter	Description
predicate	A function that takes a character and returns true if the character should be dropped, or false otherwise.

The predicate parameter is a function that defines the condition for dropping characters from the beginning of the string. The function returns a new string containing the remaining characters.

Examples for String dropWhile() function

1. Dropping Prefix While Character is a Vowel

In this example, we’ll use dropWhile() to create a substring by excluding characters from the beginning of a string while the character is a vowel.

1. Take a string value in text.
2. Define a predicate function that returns true for vowels and false for other characters.
3. Call dropWhile() function on text with the defined predicate. The function returns a new string with the prefix dropped based on the predicate condition.
4. You may print the resulting string to the console output.

Kotlin Program

fun main() {
    val text = "awesome"

    // Defining a predicate function
    val isVowel: (Char) -> Boolean = { it.lowercase() in "aeiou" }

    // Using dropWhile() to exclude characters while they are vowels
    val resultString = text.dropWhile(isVowel)

    // Printing the original string and the result
    println("Original Text:\n$text\n")
    println("Result String:\n$resultString")
}

Output

Original Text:
awesome

Result String:
wesome

Summary

In this tutorial, we’ve covered the dropWhile() function in Kotlin strings, its syntax, and how to use it to create substrings by excluding characters from the beginning of the original string based on a specified condition. This function is handy for manipulating string data by dynamically determining the exclusion criteria.