🔀 Kotlin – If…Else Expressions: Write Conditional Logic Clearly

🧲 Introduction – Why Learn Kotlin If…Else Expressions?

Conditional logic is key to any application—whether it’s checking user input, validating forms, or handling permissions. Kotlin elevates the traditional if...else by allowing it to be used not just as a statement, but also as an expression. This enables concise and readable code that assigns or returns values directly based on conditions.

🎯 In this guide, you’ll learn:

• Syntax and structure of if, if-else, and if-else-if
• How if works as both statement and expression
• Best practices for nested and complex conditions
• Real-world usage examples

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✅ Basic If Statement in Kotlin

val age = 20

if (age >= 18) {
    println("You are an adult.")
}

🟢 Output:

You are an adult.

• Executes the block only when the condition is true.

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🔁 If…Else Statement

val score = 65

if (score >= 70) {
    println("Passed")
} else {
    println("Failed")
}

🟢 Output:

Failed

• Executes one of two blocks depending on the condition.

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🔀 If…Else…If Ladder

Used when multiple conditions need to be checked.

val marks = 85

if (marks >= 90) {
    println("Grade A")
} else if (marks >= 75) {
    println("Grade B")
} else if (marks >= 60) {
    println("Grade C")
} else {
    println("Fail")
}

🟢 Output:

Grade B

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✨ Kotlin If as an Expression

In Kotlin, if can return a value—this makes it an expression rather than just a control statement.

✅ Assigning to a variable:

val num = 10
val result = if (num % 2 == 0) "Even" else "Odd"
println(result)

🟢 Output:

Even

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🧠 Expression with Blocks

You can use multi-line if blocks with return values:

val age = 21

val category = if (age < 13) {
    "Child"
} else if (age in 13..19) {
    "Teen"
} else {
    "Adult"
}

println(category)

🟢 Output:

Adult

✔️ The last expression in each block is returned.

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🧪 Nested If Statements

You can nest if conditions inside each other, but use this with caution.

val isMember = true
val hasPaid = true

if (isMember) {
    if (hasPaid) {
        println("Access Granted")
    } else {
        println("Please Pay First")
    }
} else {
    println("Membership Required")
}

🟢 Output:

Access Granted

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✅ Best Practices for if...else in Kotlin

Practice	Why It Helps
Prefer if as an expression	Makes code more concise and readable
Avoid deep nesting	Use when for cleaner multi-branch logic
Use braces {} even for one-liners	Prevents bugs in future edits
Combine conditions using && and `

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🚫 Common Mistakes with Kotlin If…Else

❌ Mistake	✅ Correction
Omitting else when it’s required	Always handle all expected conditions
Forgetting return value in blocks	Ensure the last line returns a value
Nesting too deeply	Use when for clarity
Using assignment = instead of equality ==	Always use == in conditions

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📌 Summary – Recap & Next Steps

The if...else expression in Kotlin is both powerful and expressive. It allows clean inline logic, supports value assignment, and enables better decision-making in your apps.

🔍 Key Takeaways:

• Kotlin treats if as an expression that returns a value.
• if, else if, and else blocks evaluate in order.
• Use if for two or three conditions; switch to when for more.
• Avoid nesting; prefer clean and readable expressions.

⚙️ Practical Use:
if...else expressions are essential for form validation, user permissions, business rule enforcement, and dynamic UI updates in Kotlin apps.

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❓ FAQs – Kotlin If…Else

❓ Is Kotlin’s if a statement or an expression?
✅ Kotlin allows if to be both—a traditional statement and an expression that returns a value.

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❓ Can I assign the result of an if to a variable?
✅ Yes. Kotlin supports value assignment using if:

val type = if (age > 18) "Adult" else "Minor"

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❓ What if I forget the else block in an if expression?
✅ You’ll get a compiler error if the if is used as an expression. You must cover all cases.

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❓ Should I use if...else or when?
✅ Use if...else for 2–3 branches. Use when when you have multiple cases or conditions.

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❓ Does Kotlin require parentheses around conditions?
✅ No. Parentheses are optional:

if (x > 5) { ... } // ✅

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