**Course Title:** Kotlin Programming: From Basics to Advanced Techniques **Section Title:** Control Structures and Functions **Topic:** Conditional statements: if, when. ### Introduction to Conditional Statements In programming, conditional statements are used to execute different blocks of code based on certain conditions. In Kotlin, we can use `if` and `when` statements to control the flow of our program. ### If Statement The `if` statement is a fundamental control structure in programming. It allows us to execute a block of code if a certain condition is met. #### Syntax ```kotlin if (condition) { // code to be executed if the condition is true } else { // code to be executed if the condition is false } ``` #### Example ```kotlin fun main() { val age = 25 if (age > 18) { println("You are eligible to vote.") } else { println("You are not eligible to vote.") } } ``` In this example, the condition `age > 18` is evaluated, and if it's true, the code inside the `if` block is executed. Otherwise, the code inside the `else` block is executed. #### If Expression In Kotlin, `if` can also be used as an expression, which means it can return a value. ```kotlin fun main() { val age = 25 val isEligibleToVote = if (age > 18) "Yes" else "No" println(isEligibleToVote) // prints "Yes" } ``` In this example, the `if` expression returns a string value, which is assigned to the `isEligibleToVote` variable. ### When Statement The `when` statement is a more concise and elegant way to handle multiple conditions. It's often referred to as a "switch statement" in other languages. #### Syntax ```kotlin when (expression) { value1 -> { // code to be executed if the expression matches value1 } value2 -> { // code to be executed if the expression matches value2 } else -> { // code to be executed if the expression does not match any of the values } } ``` #### Example ```kotlin fun main() { val color = "red" when (color) { "red" -> println("The color is red.") "green" -> println("The color is green.") else -> println("The color is unknown.") } } ``` In this example, the `when` statement checks the value of the `color` variable and executes the corresponding code block. #### When as an Expression Like the `if` statement, `when` can also be used as an expression. ```kotlin fun main() { val color = "red" val colorName = when (color) { "red" -> "Red" "green" -> "Green" else -> "Unknown" } println(colorName) // prints "Red" } ``` In this example, the `when` expression returns a string value, which is assigned to the `colorName` variable. ### Key Concepts * Conditional statements are used to control the flow of a program based on certain conditions. * The `if` statement is used to execute a block of code if a condition is true. * The `when` statement is used to handle multiple conditions and execute different code blocks based on the value of an expression. * Both `if` and `when` can be used as expressions, returning a value. ### Practical Takeaways * Use the `if` statement to simplify your code and make it more readable. * Use the `when` statement to handle multiple conditions and avoid nested `if` statements. * Take advantage of the expression forms of `if` and `when` to return values and simplify your code. ### Resources * [Kotlin Documentation: Control Flow](https://kotlinlang.org/docs/basic-syntax.html#control-flow) * [Kotlin Documentation: if Expression](https://kotlinlang.org/docs/basic-syntax.html#if-expression) * [Kotlin Documentation: when Expression](https://kotlinlang.org/docs/basic-syntax.html#when-expression) ### Next Topic: Loops: for, while, do-while In the next topic, we'll cover the basics of loops in Kotlin, including the `for`, `while`, and `do-while` statements. We'll explore how to use these loops to iterate over collections, repeat code blocks, and execute tasks until a condition is met. **Leave your comment below if you have any questions about conditional statements in Kotlin or if you'd like to discuss any topics related to control structures and functions.