17. String manipulation in Kotlin: Built-in functions and extensions

February 05, 2025

🧩 String Manipulation in Kotlin: Mastering Built-in Functions and Extensions

Welcome, Kotlin developers! Working with strings is a fundamental skill in programming, and Kotlin provides a powerful set of built-in functions and extension methods that make string manipulation incredibly efficient and readable. In this comprehensive guide, we'll dive deep into string handling techniques that will level up your Kotlin programming skills.

🔍 Understanding Kotlin String Basics

In Kotlin, strings are immutable objects of the String class. Unlike some other languages, Kotlin treats strings as first-class citizens with extensive built-in functionality.

// String declaration examples
val greeting = "Hello, Kotlin!"
val emptyString = ""
val multilineString = """
    This is a
    multiline string
""".trimIndent()

🛠️ Essential String Manipulation Functions

Kotlin provides a rich set of functions for string manipulation:

1. Length and Checking

val text = "Kotlin Programming"
println(text.length)  // 19
println(text.isEmpty())  // false
println(text.isNotEmpty())  // true
println(text.isBlank())  // false

2. Transformation Functions

val text = "kotlin"
println(text.uppercase())  // KOTLIN
println(text.lowercase())  // kotlin
println(text.capitalize())  // Kotlin
println(text.decapitalize())  // kotlin

3. Trimming and Cleaning

val dirtyString = "  Kotlin Rocks!  "
println(dirtyString.trim())  // "Kotlin Rocks!"
println(dirtyString.trimStart())  // "Kotlin Rocks!  "
println(dirtyString.trimEnd())  // "  Kotlin Rocks!"

🔪 Advanced String Splitting and Joining

val csvData = "John,Doe,30,Developer"
val parts = csvData.split(",")
println(parts)  // [John, Doe, 30, Developer]

val rejoined = parts.joinToString(separator = " | ")
println(rejoined)  // "John | Doe | 30 | Developer"

🔬 Substring and Searching

val text = "Kotlin is awesome"
println(text.substring(0, 6))  // "Kotlin"
println(text.startsWith("Kotlin"))  // true
println(text.contains("awesome"))  // true
println(text.indexOf("is"))  // 7

🧪 Practical Exercises

Create a function that validates email addresses using string manipulation
Implement a string reversal method without using built-in reverse functions
Write a program to count word occurrences in a given text
Develop a string compression algorithm
Create a method to convert camelCase to snake_case

Pro Tip: Always prefer Kotlin's built-in string functions over manual implementations for better performance and readability.

🚀 Performance Considerations

While Kotlin's string functions are convenient, be mindful of creating multiple string objects. For heavy string manipulations, consider using StringBuilder.

val builder = StringBuilder()
builder.append("Hello")
builder.append(" ")
builder.append("Kotlin")
val result = builder.toString()

🎓 Conclusion

Mastering string manipulation in Kotlin opens up numerous possibilities for text processing and data handling. By leveraging these built-in functions and extension methods, you can write more concise, readable, and efficient code.

#Kotlin #Programming #StringManipulation #AndroidDev

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