Kotlin Basics for Android Developers

This is a curated index of Kotlin language fundamentals covered on this site — arrays, strings, and basic control flow. Each entry below links to a focused tutorial with working code examples. If you’re new to Kotlin, start with the Control Flow section; if you already know the syntax and just need a specific array or string operation, jump straight to it.

Getting Started

• Hello, World in Kotlin — the smallest possible Kotlin program, and where to run it.
• The Kotlin main Function — how the entry point works, including the version that takes command-line arguments.
• Loop Statements — for, while, and do-while loops in Kotlin.
• Ranges — using .., until, and downTo to iterate over a sequence of values.
• Error Handling with try/catch — catching and handling exceptions.
• Throwing Exceptions — raising your own exceptions with throw.
• Creating a Custom Exception — defining your own exception classes for domain-specific errors.

Arrays

Kotlin arrays are fixed-size, and the standard library gives you a dedicated type for each primitive (IntArray, ByteArray, etc.) alongside the generic Array<T>.

• Kotlin Array Example — the basics of declaring and reading from an array.
• Creating Arrays — the different ways to construct an array, including arrayOf and the size-and-initializer constructor.
• Creating Integer Arrays — using IntArray and intArrayOf specifically.
• Creating Byte Arrays — working with ByteArray, useful for raw binary data.
• Creating an Empty Array — initializing an array with no elements or a fixed size of zero-values.
• Getting the First Element — safely reading the first item, including the firstOrNull() alternative.
• Array Size — reading an array’s length with the size property.
• Creating a String Array — declaring an Array<String>, Kotlin’s array type for text values.

Strings

Kotlin strings are immutable and come with template support ("$name") built into the language.

• String Operations — an overview of common string methods.
• Initializing a String — the basic ways to declare and assign a string value.
• Creating an Empty String — using "" versus String().
• Defining String Constants — using const val for compile-time string constants.
• Finding String Length — reading a string’s length property.
• Comparing Strings — structural (==) versus referential (===) equality for strings.
• Checking If Two Strings Are Equal — a focused walkthrough of equals() and case-insensitive comparison.
• Multiline Strings — triple-quoted raw strings for multi-line text and templates.
• Printing a String — print() versus println().

What’s Next

These fundamentals cover plain Kotlin. If you’re building Android UI, the modern approach is Jetpack Compose rather than XML layouts — we’re publishing a dedicated Compose state management guide soon. For now, see our Flutter Widgets Guide if you’re working cross-platform.