- 01Getting Started
- 02Your First Output (println)
- 03Working with Variables
- 04Conditionals (if statements)
- 05Loops (for statements)
- 06Writing a Function
- 07Working with Lists
- 08Loops (while statements)
- 09Classes (Object-Oriented Programming)
- 10Error Handling (try-catch)
- 11Sorting a List
- 12Recursive Functions
- 13Using the Standard Library
- 14The when Statement
- 15The if Expression
- 16Inheritance (Extending a Class)
- 17Writing Comments
- 18Logical Operators (&&, ||, !)
- 19Constants (const val)
- 20Splitting and Joining Strings (split, joinToString)
- 21Writing Null-Safe Code (the ?: Elvis operator)
- 22Searching a List (contains, find)
- 23Transforming a List (map)
- 24Two-Dimensional Lists (Tabular Data)
- 25Writing a Custom Exception Class
- 26Default Parameter Values
- 27Working with Set
- 28Checking Correctness (Your First Step into Testing)
- 29Higher-Order Functions (Passing a Function as an Argument)
- 30Stacks and Queues (Basic Data Structures)
- 31Type Conversion (Casting) Basics
- 32Intro to Regular Expressions (Pattern Matching)
- 33The Binary Search Algorithm
- 34Building a Caesar Cipher (a Character-Shifting Cipher)
- 35Understanding How Bubble Sort Works
- 36Building and Displaying Dates (Basic Year/Month/Day Operations)
- 37Writing Multiple Test Cases Together
- 38Speeding Up Calculations with Memoization (Caching)
- 39Normalizing Strings (trim, Unifying Case)
- 40Shallow Copy vs. Deep Copy
- 41Enum (Enumerated Types) Basics
- 42Flattening a List
- 43Reversing a String and Checking for Palindromes
- 44Pairing Up Two Lists (the zip operation)
- 45Rounding Numbers (floor, ceil, roundToInt)
- 46Multi-Line Strings (Triple Quotes)
- 47Functions That Return Multiple Values (Pair)
- 48Finding the GCD and LCM (the Euclidean Algorithm)
- 49Formatting Numbers (Padding Digits, Decimal Places)
- 50Cleanup Logic with try/catch/finally
- 51Writing Generic Functions
- 52File Reading and Writing Basics
- 53Generating Random Numbers
- 54Bitwise Operators (and, or, xor, shifts)
- 55Reading Command-Line Arguments
- 56Waiting for a Fixed Amount of Time (Thread.sleep)
- 57Watch Out for Floating-Point Rounding Errors
- 58Reading from Standard Input
- 59FizzBuzz (the Classic Practice Problem)
- 60Checking Whether a Number Is Prime
- 61Set Operations with Set (Union, Intersection, Difference)
- 62Converting Number Bases (Binary, Hex)
- 63Checking Balanced Parentheses (an Application of Stacks)
- 64Checking Whether Two Words Are Anagrams
- 65Checking Whether a Year Is a Leap Year
- 66Converting Temperature (Celsius to Fahrenheit)
- 67Prime Factorization
- 68[Applied] Build a Simple Inventory Management Tool
Reading Command-Line Arguments
In this lesson you will learn how to read command-line arguments in Kotlin, so values can be passed in from outside when the program runs. This is for anyone searching for "Kotlin command-line arguments how to use".
Declaring fun main(args: Array<String>) gives your main function an args array holding the command-line arguments. It is essential whenever you want a command-line tool whose options can be switched at run time.
The sample code checks whether any arguments were supplied with args.isNotEmpty(), and uses an if expression to take args[0] as the name when there is one and fall back to "Anonymous" when there is not.
A common stumbling block for beginners is forgetting the case where no argument was supplied. Reaching straight for args[0] errors out when nothing was passed, so check with args.isNotEmpty() or args.size first.
In real-world development this also serves as the foundation of simple automation scripts that branch on the values supplied at run time.
๐งช This site can't compile or run Kotlin directly, so it checks on the spot whether what you typed matches the reference code (scoring happens entirely in your browser โ nothing is sent anywhere).