Kotlin Tutorial (Beginner to Advanced)

∙ Chapter 001

Kotlin Tutorial

Learn Kotlin Tutorial with a small example you can edit and run.

📝Syntax

fun main(){
  // ...
}

⚡Example (Edit & Run)

Edit the Kotlin code below and click Run. The output panel shows the extracted Expected Output notes (or simple prints).

tutorial.kt

📝 Edit Code

👁 Output

💡 Tip: keep a // Expected Output: line so the output panel has something to show.

🔍Line-by-line

Line	Meaning
`fun main() {`	Program entry point.
`println("Welcome to Kotlin")`	Prints output.
`}`	Kotlin line.

🏢Real-world

1Kotlin is widely used for Android apps and JVM backends.

⚠Common Mistakes

1Mixing up val vs var and mutating unexpectedly.

✅Best Practices

1Prefer val by default and keep functions small and clear.

📖Summary & Practice

1Edit the example and rerun to learn faster.
2Use readable Kotlin first; optimize later.

💡Practice: answer the questions below, then modify the example to match your answers.

1Change one value and predict the output.
2Add one edge case and handle it.
3Explain the rule in 1 sentence.

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∙ Chapter 002

Kotlin HOME

Learn Kotlin HOME with a small example you can edit and run.

📝Syntax

fun main(){
  // ...
}

⚡Example (Edit & Run)

Edit the Kotlin code below and click Run. The output panel shows the extracted Expected Output notes (or simple prints).

home.kt

📝 Edit Code

👁 Output

💡 Tip: keep a // Expected Output: line so the output panel has something to show.

🔍Line-by-line

Line	Meaning
`fun main() {`	Program entry point.
`println("Welcome to Kotlin")`	Prints output.
`}`	Kotlin line.

🏢Real-world

1Kotlin is widely used for Android apps and JVM backends.

⚠Common Mistakes

1Mixing up val vs var and mutating unexpectedly.

✅Best Practices

1Prefer val by default and keep functions small and clear.

📖Summary & Practice

1Edit the example and rerun to learn faster.
2Use readable Kotlin first; optimize later.

💡Practice: answer the questions below, then modify the example to match your answers.

1Change one value and predict the output.
2Add one edge case and handle it.
3Explain the rule in 1 sentence.

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∙ Chapter 003

Kotlin Intro

Learn Kotlin Intro with a small example you can edit and run.

📝Syntax

fun main(){
  // ...
}

⚡Example (Edit & Run)

Edit the Kotlin code below and click Run. The output panel shows the extracted Expected Output notes (or simple prints).

intro.kt

📝 Edit Code

👁 Output

💡 Tip: keep a // Expected Output: line so the output panel has something to show.

🔍Line-by-line

Line	Meaning
`fun main() {`	Program entry point.
`println("Welcome to Kotlin")`	Prints output.
`}`	Kotlin line.

🏢Real-world

1Kotlin is widely used for Android apps and JVM backends.

⚠Common Mistakes

1Mixing up val vs var and mutating unexpectedly.

✅Best Practices

1Prefer val by default and keep functions small and clear.

📖Summary & Practice

1Edit the example and rerun to learn faster.
2Use readable Kotlin first; optimize later.

💡Practice: answer the questions below, then modify the example to match your answers.

1Change one value and predict the output.
2Add one edge case and handle it.
3Explain the rule in 1 sentence.

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∙ Chapter 004

Kotlin Get Started

Learn Kotlin Get Started with a small example you can edit and run.

📝Syntax

fun main(){
  // ...
}

⚡Example (Edit & Run)

Edit the Kotlin code below and click Run. The output panel shows the extracted Expected Output notes (or simple prints).

get-started.kt

📝 Edit Code

👁 Output

💡 Tip: keep a // Expected Output: line so the output panel has something to show.

🔍Line-by-line

Line	Meaning
`fun main() {`	Program entry point.
`println("Welcome to Kotlin")`	Prints output.
`}`	Kotlin line.

🏢Real-world

1Kotlin is widely used for Android apps and JVM backends.

⚠Common Mistakes

1Mixing up val vs var and mutating unexpectedly.

✅Best Practices

1Prefer val by default and keep functions small and clear.

📖Summary & Practice

1Edit the example and rerun to learn faster.
2Use readable Kotlin first; optimize later.

💡Practice: answer the questions below, then modify the example to match your answers.

1Change one value and predict the output.
2Add one edge case and handle it.
3Explain the rule in 1 sentence.

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∙ Chapter 005

Kotlin Syntax

Learn Kotlin Syntax with a small example you can edit and run.

📝Syntax

fun main(){
  // ...
}

⚡Example (Edit & Run)

Edit the Kotlin code below and click Run. The output panel shows the extracted Expected Output notes (or simple prints).

syntax.kt

📝 Edit Code

👁 Output

💡 Tip: keep a // Expected Output: line so the output panel has something to show.

🔍Line-by-line

Line	Meaning
`fun main() {`	Program entry point.
`val score = 82`	Declares a variable (val = immutable, var = mutable).
`val result = if (score >= 75) "Pass" else "Fail"`	Declares a variable (val = immutable, var = mutable).
`println(result)`	Prints output.
`}`	Kotlin line.

🏢Real-world

1Kotlin is widely used for Android apps and JVM backends.

⚠Common Mistakes

1Mixing up val vs var and mutating unexpectedly.

✅Best Practices

1Prefer val by default and keep functions small and clear.

📖Summary & Practice

1Edit the example and rerun to learn faster.
2Use readable Kotlin first; optimize later.

💡Practice: answer the questions below, then modify the example to match your answers.

1Change one value and predict the output.
2Add one edge case and handle it.
3Explain the rule in 1 sentence.

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∙ Chapter 006

Kotlin Output

Learn Kotlin Output with a small example you can edit and run.

📝Syntax

println("Hello")
print("No newline")

⚡Example (Edit & Run)

Edit the Kotlin code below and click Run. The output panel shows the extracted Expected Output notes (or simple prints).

output.kt

📝 Edit Code

👁 Output

💡 Tip: keep a // Expected Output: line so the output panel has something to show.

🔍Line-by-line

Line	Meaning
`fun main() {`	Program entry point.
`print("Hi")`	Prints output.
`print(" ")`	Prints output.
`println("Kotlin")`	Prints output.
`}`	Kotlin line.

🏢Real-world

1Kotlin is widely used for Android apps and JVM backends.

⚠Common Mistakes

1Mixing up val vs var and mutating unexpectedly.

✅Best Practices

1Prefer val by default and keep functions small and clear.

📖Summary & Practice

1Edit the example and rerun to learn faster.
2Use readable Kotlin first; optimize later.

💡Practice: answer the questions below, then modify the example to match your answers.

1Change one value and predict the output.
2Add one edge case and handle it.
3Explain the rule in 1 sentence.

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Keywords (topic intent):

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∙ Chapter 007

Kotlin Comments

Learn Kotlin Comments with a small example you can edit and run.

📝Syntax

// single-line
/* multi-line */

⚡Example (Edit & Run)

Edit the Kotlin code below and click Run. The output panel shows the extracted Expected Output notes (or simple prints).

comments.kt

📝 Edit Code

👁 Output

💡 Tip: keep a // Expected Output: line so the output panel has something to show.

🔍Line-by-line

Line	Meaning
`fun main() {`	Program entry point.
`/* Multi-line`	Kotlin line.
`comment */`	Kotlin line.
`println("Comments don't change output")`	Prints output.
`}`	Kotlin line.

🏢Real-world

1Kotlin is widely used for Android apps and JVM backends.

⚠Common Mistakes

1Mixing up val vs var and mutating unexpectedly.

✅Best Practices

1Prefer val by default and keep functions small and clear.

📖Summary & Practice

1Edit the example and rerun to learn faster.
2Use readable Kotlin first; optimize later.

💡Practice: answer the questions below, then modify the example to match your answers.

1Change one value and predict the output.
2Add one edge case and handle it.
3Explain the rule in 1 sentence.

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∙ Chapter 008

Kotlin Variables

Learn Kotlin Variables with a small example you can edit and run.

📝Syntax

val name: String = "Mana"
var age = 21

⚡Example (Edit & Run)

Edit the Kotlin code below and click Run. The output panel shows the extracted Expected Output notes (or simple prints).

variables.kt

📝 Edit Code

👁 Output

💡 Tip: keep a // Expected Output: line so the output panel has something to show.

🔍Line-by-line

Line	Meaning
`fun main() {`	Program entry point.
`val name = "Mana"`	Declares a variable (val = immutable, var = mutable).
`var level = 1`	Declares a variable (val = immutable, var = mutable).
`level += 1`	Kotlin line.
`println("$name level $level")`	Prints output.
`}`	Kotlin line.

🏢Real-world

1Kotlin is widely used for Android apps and JVM backends.

⚠Common Mistakes

1Mixing up val vs var and mutating unexpectedly.

✅Best Practices

1Prefer val by default and keep functions small and clear.

📖Summary & Practice

1Edit the example and rerun to learn faster.
2Use readable Kotlin first; optimize later.

💡Practice: answer the questions below, then modify the example to match your answers.

1Change one value and predict the output.
2Add one edge case and handle it.
3Explain the rule in 1 sentence.

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∙ Chapter 009

Kotlin Data Types

Learn Kotlin Data Types with a small example you can edit and run.

📝Syntax

val n: Int = 7
val pi: Double = 3.14
val ok: Boolean = true

⚡Example (Edit & Run)

Edit the Kotlin code below and click Run. The output panel shows the extracted Expected Output notes (or simple prints).

data-types.kt

📝 Edit Code

👁 Output

💡 Tip: keep a // Expected Output: line so the output panel has something to show.

🔍Line-by-line

Line	Meaning
`fun main() {`	Program entry point.
`val a: Int = 10`	Declares a variable (val = immutable, var = mutable).
`val b: Double = 3.5`	Declares a variable (val = immutable, var = mutable).
`val ok: Boolean = true`	Declares a variable (val = immutable, var = mutable).
`val ch: Char = 'A'`	Declares a variable (val = immutable, var = mutable).
`println("$a, $b, $ok, $ch")`	Prints output.
`}`	Kotlin line.

🏢Real-world

1Kotlin is widely used for Android apps and JVM backends.

⚠Common Mistakes

1Mixing up val vs var and mutating unexpectedly.

✅Best Practices

1Prefer val by default and keep functions small and clear.

📖Summary & Practice

1Edit the example and rerun to learn faster.
2Use readable Kotlin first; optimize later.

💡Practice: answer the questions below, then modify the example to match your answers.

1Change one value and predict the output.
2Add one edge case and handle it.
3Explain the rule in 1 sentence.

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∙ Chapter 010

Kotlin Operators

Learn Kotlin Operators with a small example you can edit and run.

📝Syntax

val sum = a + b
val gt = a > b
val mod = a % b

⚡Example (Edit & Run)

Edit the Kotlin code below and click Run. The output panel shows the extracted Expected Output notes (or simple prints).

operators.kt

📝 Edit Code

👁 Output

💡 Tip: keep a // Expected Output: line so the output panel has something to show.

🔍Line-by-line

Line	Meaning
`fun main() {`	Program entry point.
`val a = 7`	Declares a variable (val = immutable, var = mutable).
`val b = 3`	Declares a variable (val = immutable, var = mutable).
`println(a + b)`	Prints output.
`}`	Kotlin line.

🏢Real-world

1Kotlin is widely used for Android apps and JVM backends.

⚠Common Mistakes

1Mixing up val vs var and mutating unexpectedly.

✅Best Practices

1Prefer val by default and keep functions small and clear.

📖Summary & Practice

1Edit the example and rerun to learn faster.
2Use readable Kotlin first; optimize later.

💡Practice: answer the questions below, then modify the example to match your answers.

1Change one value and predict the output.
2Add one edge case and handle it.
3Explain the rule in 1 sentence.

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∙ Chapter 011

Kotlin Strings

Learn Kotlin Strings with a small example you can edit and run.

📝Syntax

val s = "Kotlin"
println("$s length=${s.length}")

⚡Example (Edit & Run)

Edit the Kotlin code below and click Run. The output panel shows the extracted Expected Output notes (or simple prints).

strings.kt

📝 Edit Code

👁 Output

💡 Tip: keep a // Expected Output: line so the output panel has something to show.

🔍Line-by-line

Line	Meaning
`fun main() {`	Program entry point.
`val name = "Mana"`	Declares a variable (val = immutable, var = mutable).
`val msg = "$name Coding"`	Declares a variable (val = immutable, var = mutable).
`println(msg)`	Prints output.
`println(msg.length)`	Prints output.
`}`	Kotlin line.

🏢Real-world

1Strings are used for UI text, logs, and building messages.

⚠Common Mistakes

1Concatenating in loops instead of using templates/builders.

✅Best Practices

1Use string templates and keep formatting consistent.

📖Summary & Practice

1Edit the example and rerun to learn faster.
2Use readable Kotlin first; optimize later.

💡Practice: answer the questions below, then modify the example to match your answers.

1Change one value and predict the output.
2Add one edge case and handle it.
3Explain the rule in 1 sentence.

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Keywords (topic intent):

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∙ Chapter 012

Kotlin Booleans

Learn Kotlin Booleans with a small example you can edit and run.

📝Syntax

val ok = (a >= 10) && (b < 5)

⚡Example (Edit & Run)

Edit the Kotlin code below and click Run. The output panel shows the extracted Expected Output notes (or simple prints).

booleans.kt

📝 Edit Code

👁 Output

💡 Tip: keep a // Expected Output: line so the output panel has something to show.

🔍Line-by-line

Line	Meaning
`fun main() {`	Program entry point.
`val a = 10`	Declares a variable (val = immutable, var = mutable).
`val b = 2`	Declares a variable (val = immutable, var = mutable).
`val ok = (a >= 10) && (b < 5)`	Declares a variable (val = immutable, var = mutable).
`println(ok)`	Prints output.
`}`	Kotlin line.

🏢Real-world

1Kotlin is widely used for Android apps and JVM backends.

⚠Common Mistakes

1Mixing up val vs var and mutating unexpectedly.

✅Best Practices

1Prefer val by default and keep functions small and clear.

📖Summary & Practice

1Edit the example and rerun to learn faster.
2Use readable Kotlin first; optimize later.

💡Practice: answer the questions below, then modify the example to match your answers.

1Change one value and predict the output.
2Add one edge case and handle it.
3Explain the rule in 1 sentence.

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Keywords (topic intent):

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∙ Chapter 013

Kotlin If...Else

Learn Kotlin If...Else with a small example you can edit and run.

📝Syntax

val label = if (score >= 75) "Pass" else "Fail"

⚡Example (Edit & Run)

Edit the Kotlin code below and click Run. The output panel shows the extracted Expected Output notes (or simple prints).

if-else.kt

📝 Edit Code

👁 Output

💡 Tip: keep a // Expected Output: line so the output panel has something to show.

🔍Line-by-line

Line	Meaning
`fun main() {`	Program entry point.
`val score = 75`	Declares a variable (val = immutable, var = mutable).
`if (score >= 90) println("A")`	Prints output.
`else if (score >= 75) println("B")`	Prints output.
`else println("C")`	Prints output.
`}`	Kotlin line.

🏢Real-world

1Control flow powers validation, UI state, and business rules.

⚠Common Mistakes

1Forgetting edge cases (empty lists, boundaries).

✅Best Practices

1Write readable conditions and test boundaries.

📖Summary & Practice

1Edit the example and rerun to learn faster.
2Use readable Kotlin first; optimize later.

💡Practice: answer the questions below, then modify the example to match your answers.

1Change one value and predict the output.
2Add one edge case and handle it.
3Explain the rule in 1 sentence.

📈SEO

Keywords (topic intent):

Kotlin JVM Kotlin If...Else

∙ Chapter 014

Kotlin When

Learn Kotlin When with a small example you can edit and run.

📝Syntax

val msg = when (day) {
  1 -> "Mon"
  else -> "Other"
}

⚡Example (Edit & Run)

Edit the Kotlin code below and click Run. The output panel shows the extracted Expected Output notes (or simple prints).

when.kt

📝 Edit Code

👁 Output

💡 Tip: keep a // Expected Output: line so the output panel has something to show.

🔍Line-by-line

Line	Meaning
`fun main() {`	Program entry point.
`val day = 3`	Declares a variable (val = immutable, var = mutable).
`val name = when (day) {`	Declares a variable (val = immutable, var = mutable).
`1 -> "Mon"`	Kotlin line.
`2 -> "Tue"`	Kotlin line.
`3 -> "Wed"`	Kotlin line.
`else -> "Other"`	Kotlin line.
`}`	Kotlin line.
`println(name)`	Prints output.
`}`	Kotlin line.

🏢Real-world

1Control flow powers validation, UI state, and business rules.

⚠Common Mistakes

1Forgetting edge cases (empty lists, boundaries).

✅Best Practices

1Write readable conditions and test boundaries.

📖Summary & Practice

1Edit the example and rerun to learn faster.
2Use readable Kotlin first; optimize later.

💡Practice: answer the questions below, then modify the example to match your answers.

1Change one value and predict the output.
2Add one edge case and handle it.
3Explain the rule in 1 sentence.

📈SEO

Keywords (topic intent):

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∙ Chapter 015

Kotlin While Loop

Learn Kotlin While Loop with a small example you can edit and run.

📝Syntax

while (i <= 5) { i++ }

⚡Example (Edit & Run)

Edit the Kotlin code below and click Run. The output panel shows the extracted Expected Output notes (or simple prints).

while-loop.kt

📝 Edit Code

👁 Output

💡 Tip: keep a // Expected Output: line so the output panel has something to show.

🔍Line-by-line

Line	Meaning
`fun main() {`	Program entry point.
`var n = 1`	Declares a variable (val = immutable, var = mutable).
`var sum = 0`	Declares a variable (val = immutable, var = mutable).
`while (n <= 5) {`	Loop while condition is true.
`sum += n`	Kotlin line.
`n++`	Kotlin line.
`}`	Kotlin line.
`println(sum)`	Prints output.
`}`	Kotlin line.

🏢Real-world

1Control flow powers validation, UI state, and business rules.

⚠Common Mistakes

1Forgetting edge cases (empty lists, boundaries).

✅Best Practices

1Write readable conditions and test boundaries.

📖Summary & Practice

1Edit the example and rerun to learn faster.
2Use readable Kotlin first; optimize later.

💡Practice: answer the questions below, then modify the example to match your answers.

1Change one value and predict the output.
2Add one edge case and handle it.
3Explain the rule in 1 sentence.

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Keywords (topic intent):

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∙ Chapter 016

Kotlin Break/Continue

Learn Kotlin Break/Continue with a small example you can edit and run.

📝Syntax

for (i in 1..10) {
  if (i == 3) continue
  if (i == 5) break
}

⚡Example (Edit & Run)

Edit the Kotlin code below and click Run. The output panel shows the extracted Expected Output notes (or simple prints).

break-continue.kt

📝 Edit Code

👁 Output

💡 Tip: keep a // Expected Output: line so the output panel has something to show.

🔍Line-by-line

Line	Meaning
`fun main() {`	Program entry point.
`for (i in 1..6) {`	Loop over a range/collection.
`if (i == 3) continue`	Conditional branch.
`if (i == 5) break`	Conditional branch.
`println(i)`	Prints output.
`}`	Kotlin line.
`}`	Kotlin line.

🏢Real-world

1Control flow powers validation, UI state, and business rules.

⚠Common Mistakes

1Forgetting edge cases (empty lists, boundaries).

✅Best Practices

1Write readable conditions and test boundaries.

📖Summary & Practice

1Edit the example and rerun to learn faster.
2Use readable Kotlin first; optimize later.

💡Practice: answer the questions below, then modify the example to match your answers.

1Change one value and predict the output.
2Add one edge case and handle it.
3Explain the rule in 1 sentence.

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Keywords (topic intent):

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∙ Chapter 017

Kotlin Arrays

Learn Kotlin Arrays with a small example you can edit and run.

📝Syntax

val a = intArrayOf(1, 2, 3)
val b = arrayOf("A", "B")

⚡Example (Edit & Run)

Edit the Kotlin code below and click Run. The output panel shows the extracted Expected Output notes (or simple prints).

arrays.kt

📝 Edit Code

👁 Output

💡 Tip: keep a // Expected Output: line so the output panel has something to show.

🔍Line-by-line

Line	Meaning
`fun main() {`	Program entry point.
`val nums = intArrayOf(1, 2, 3, 4)`	Declares a variable (val = immutable, var = mutable).
`var sum = 0`	Declares a variable (val = immutable, var = mutable).
`for (x in nums) sum += x`	Loop over a range/collection.
`println(sum)`	Prints output.
`}`	Kotlin line.

🏢Real-world

1Kotlin is widely used for Android apps and JVM backends.

⚠Common Mistakes

1Mixing up val vs var and mutating unexpectedly.

✅Best Practices

1Prefer val by default and keep functions small and clear.

📖Summary & Practice

1Edit the example and rerun to learn faster.
2Use readable Kotlin first; optimize later.

💡Practice: answer the questions below, then modify the example to match your answers.

1Change one value and predict the output.
2Add one edge case and handle it.
3Explain the rule in 1 sentence.

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Keywords (topic intent):

Kotlin JVM Kotlin Arrays

∙ Chapter 018

Kotlin For Loop

Learn Kotlin For Loop with a small example you can edit and run.

📝Syntax

for (i in 1..3) println(i)

⚡Example (Edit & Run)

Edit the Kotlin code below and click Run. The output panel shows the extracted Expected Output notes (or simple prints).

for-loop.kt

📝 Edit Code

👁 Output

💡 Tip: keep a // Expected Output: line so the output panel has something to show.

🔍Line-by-line

Line	Meaning
`fun main() {`	Program entry point.
`for (i in 1..3) {`	Loop over a range/collection.
`print("i=$i ")`	Prints output.
`}`	Kotlin line.
`}`	Kotlin line.

🏢Real-world

1Control flow powers validation, UI state, and business rules.

⚠Common Mistakes

1Forgetting edge cases (empty lists, boundaries).

✅Best Practices

1Write readable conditions and test boundaries.

📖Summary & Practice

1Edit the example and rerun to learn faster.
2Use readable Kotlin first; optimize later.

💡Practice: answer the questions below, then modify the example to match your answers.

1Change one value and predict the output.
2Add one edge case and handle it.
3Explain the rule in 1 sentence.

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Keywords (topic intent):

Kotlin JVM Kotlin For Loop

∙ Chapter 019

Kotlin Ranges

Learn Kotlin Ranges with a small example you can edit and run.

📝Syntax

for (i in 1..10 step 2) println(i)

⚡Example (Edit & Run)

Edit the Kotlin code below and click Run. The output panel shows the extracted Expected Output notes (or simple prints).

ranges.kt

📝 Edit Code

👁 Output

💡 Tip: keep a // Expected Output: line so the output panel has something to show.

🔍Line-by-line

Line	Meaning
`fun main() {`	Program entry point.
`for (i in 1..10 step 2) {`	Loop over a range/collection.
`print("$i ")`	Prints output.
`}`	Kotlin line.
`}`	Kotlin line.

🏢Real-world

1Control flow powers validation, UI state, and business rules.

⚠Common Mistakes

1Forgetting edge cases (empty lists, boundaries).

✅Best Practices

1Write readable conditions and test boundaries.

📖Summary & Practice

1Edit the example and rerun to learn faster.
2Use readable Kotlin first; optimize later.

💡Practice: answer the questions below, then modify the example to match your answers.

1Change one value and predict the output.
2Add one edge case and handle it.
3Explain the rule in 1 sentence.

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Keywords (topic intent):

Kotlin JVM Kotlin Ranges

∙ Chapter 020

Kotlin Functions

Learn Kotlin Functions with a small example you can edit and run.

📝Syntax

fun add(a: Int, b: Int): Int = a + b

⚡Example (Edit & Run)

Edit the Kotlin code below and click Run. The output panel shows the extracted Expected Output notes (or simple prints).

functions.kt

📝 Edit Code

👁 Output

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🔍Line-by-line

Line	Meaning
`fun add(a: Int, b: Int): Int {`	Declares a function.
`return a + b`	Kotlin line.
`}`	Kotlin line.
`fun main() {`	Program entry point.
`println(add(4, 6))`	Prints output.
`}`	Kotlin line.

🏢Real-world

1Functions help you reuse logic and keep code DRY.

⚠Common Mistakes

1Using unclear names and too many parameters.

✅Best Practices

1Prefer small, pure functions with clear inputs/outputs.

📖Summary & Practice

1Edit the example and rerun to learn faster.
2Use readable Kotlin first; optimize later.

💡Practice: answer the questions below, then modify the example to match your answers.

1Change one value and predict the output.
2Add one edge case and handle it.
3Explain the rule in 1 sentence.

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Kotlin JVM Kotlin Functions

∙ Chapter 021

Kotlin Classes

Learn Kotlin Classes with a small example you can edit and run.

📝Syntax

class Person(val name: String) {
  fun hi() = println("Hi $name")
}

⚡Example (Edit & Run)

Edit the Kotlin code below and click Run. The output panel shows the extracted Expected Output notes (or simple prints).

classes.kt

📝 Edit Code

👁 Output

💡 Tip: keep a // Expected Output: line so the output panel has something to show.

🔍Line-by-line

Line	Meaning
`class Person(val name: String) {`	Declares a class.
`fun greet() { println("Hello, $name!") }`	Declares a function.
`}`	Kotlin line.
`fun main() {`	Program entry point.
`val p = Person("Developer")`	Declares a variable (val = immutable, var = mutable).
`p.greet()`	Kotlin line.
`}`	Kotlin line.

🏢Real-world

1Classes model app domain objects and reusable components.

⚠Common Mistakes

1Overusing inheritance instead of composition.

✅Best Practices

1Keep classes focused; use inheritance only when it fits.

📖Summary & Practice

1Edit the example and rerun to learn faster.
2Use readable Kotlin first; optimize later.

💡Practice: answer the questions below, then modify the example to match your answers.

1Change one value and predict the output.
2Add one edge case and handle it.
3Explain the rule in 1 sentence.

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Keywords (topic intent):

Kotlin JVM Kotlin Classes

∙ Chapter 022

Kotlin OOP

Learn Kotlin OOP with a small example you can edit and run.

📝Syntax

class Person(val name: String) {
  fun hi() = println("Hi $name")
}

⚡Example (Edit & Run)

Edit the Kotlin code below and click Run. The output panel shows the extracted Expected Output notes (or simple prints).

oop.kt

📝 Edit Code

👁 Output

💡 Tip: keep a // Expected Output: line so the output panel has something to show.

🔍Line-by-line

Line	Meaning
`class Person(val name: String) {`	Declares a class.
`fun greet() { println("Hello, $name!") }`	Declares a function.
`}`	Kotlin line.
`fun main() {`	Program entry point.
`val p = Person("Developer")`	Declares a variable (val = immutable, var = mutable).
`p.greet()`	Kotlin line.
`}`	Kotlin line.

🏢Real-world

1Classes model app domain objects and reusable components.

⚠Common Mistakes

1Overusing inheritance instead of composition.

✅Best Practices

1Keep classes focused; use inheritance only when it fits.

📖Summary & Practice

1Edit the example and rerun to learn faster.
2Use readable Kotlin first; optimize later.

💡Practice: answer the questions below, then modify the example to match your answers.

1Change one value and predict the output.
2Add one edge case and handle it.
3Explain the rule in 1 sentence.

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Keywords (topic intent):

Kotlin JVM Kotlin OOP

∙ Chapter 023

Kotlin Classes/Objects

Learn Kotlin Classes/Objects with a small example you can edit and run.

📝Syntax

class Person(val name: String) {
  fun hi() = println("Hi $name")
}

⚡Example (Edit & Run)

Edit the Kotlin code below and click Run. The output panel shows the extracted Expected Output notes (or simple prints).

classes-objects.kt

📝 Edit Code

👁 Output

💡 Tip: keep a // Expected Output: line so the output panel has something to show.

🔍Line-by-line

Line	Meaning
`class User(val name: String)`	Declares a class.
`fun main() {`	Program entry point.
`val u = User("Mana")`	Declares a variable (val = immutable, var = mutable).
`println(u.name)`	Prints output.
`}`	Kotlin line.

🏢Real-world

1Classes model app domain objects and reusable components.

⚠Common Mistakes

1Overusing inheritance instead of composition.

✅Best Practices

1Keep classes focused; use inheritance only when it fits.

📖Summary & Practice

1Edit the example and rerun to learn faster.
2Use readable Kotlin first; optimize later.

💡Practice: answer the questions below, then modify the example to match your answers.

1Change one value and predict the output.
2Add one edge case and handle it.
3Explain the rule in 1 sentence.

📈SEO

Keywords (topic intent):

Kotlin JVM Kotlin Classes/Objects

∙ Chapter 024

Kotlin Constructors

Learn Kotlin Constructors with a small example you can edit and run.

📝Syntax

class User(val name: String) { /* primary ctor */ }

⚡Example (Edit & Run)

Edit the Kotlin code below and click Run. The output panel shows the extracted Expected Output notes (or simple prints).

constructors.kt

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👁 Output

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🔍Line-by-line

Line	Meaning
`class User(val name: String, var level: Int) {`	Declares a class.
`fun up() { level++ }`	Declares a function.
`}`	Kotlin line.
`fun main() {`	Program entry point.
`val u = User("Mana", 1)`	Declares a variable (val = immutable, var = mutable).
`u.up()`	Kotlin line.
`println("${u.name} level ${u.level}")`	Prints output.
`}`	Kotlin line.

🏢Real-world

1Classes model app domain objects and reusable components.

⚠Common Mistakes

1Overusing inheritance instead of composition.

✅Best Practices

1Keep classes focused; use inheritance only when it fits.

📖Summary & Practice

1Edit the example and rerun to learn faster.
2Use readable Kotlin first; optimize later.

💡Practice: answer the questions below, then modify the example to match your answers.

1Change one value and predict the output.
2Add one edge case and handle it.
3Explain the rule in 1 sentence.

📈SEO

Keywords (topic intent):

Kotlin JVM Kotlin Constructors

∙ Chapter 025

Kotlin Class Functions

Learn Kotlin Class Functions with a small example you can edit and run.

📝Syntax

fun add(a: Int, b: Int): Int = a + b

⚡Example (Edit & Run)

Edit the Kotlin code below and click Run. The output panel shows the extracted Expected Output notes (or simple prints).

class-functions.kt

📝 Edit Code

👁 Output

💡 Tip: keep a // Expected Output: line so the output panel has something to show.

🔍Line-by-line

Line	Meaning
`class Counter {`	Declares a class.
`private var n = 0`	Kotlin line.
`fun inc() { n++ }`	Declares a function.
`fun value(): Int = n`	Declares a function.
`}`	Kotlin line.
`fun main() {`	Program entry point.
`val c = Counter()`	Declares a variable (val = immutable, var = mutable).
`c.inc(); c.inc()`	Kotlin line.
`println(c.value())`	Prints output.
`}`	Kotlin line.

🏢Real-world

1Functions help you reuse logic and keep code DRY.

⚠Common Mistakes

1Using unclear names and too many parameters.

✅Best Practices

1Prefer small, pure functions with clear inputs/outputs.

📖Summary & Practice

1Edit the example and rerun to learn faster.
2Use readable Kotlin first; optimize later.

💡Practice: answer the questions below, then modify the example to match your answers.

1Change one value and predict the output.
2Add one edge case and handle it.
3Explain the rule in 1 sentence.

📈SEO

Keywords (topic intent):

Kotlin JVM Kotlin Class Functions

∙ Chapter 026

Kotlin Inheritance

Learn Kotlin Inheritance with a small example you can edit and run.

📝Syntax

open class Animal { open fun speak(){} }
class Dog : Animal() { override fun speak(){} }

⚡Example (Edit & Run)

Edit the Kotlin code below and click Run. The output panel shows the extracted Expected Output notes (or simple prints).

inheritance.kt

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👁 Output

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🔍Line-by-line

Line	Meaning
`open class Animal {`	Declares a class that can be inherited.
`open fun speak() { println("Animal") }`	Prints output.
`}`	Kotlin line.
`class Dog : Animal() {`	Declares a class.
`override fun speak() { println("Woof") }`	Prints output.
`}`	Kotlin line.
`fun main() {`	Program entry point.
`val a: Animal = Dog()`	Declares a variable (val = immutable, var = mutable).
`a.speak()`	Kotlin line.
`}`	Kotlin line.

🏢Real-world

1Classes model app domain objects and reusable components.

⚠Common Mistakes

1Overusing inheritance instead of composition.

✅Best Practices

1Keep classes focused; use inheritance only when it fits.

📖Summary & Practice

1Edit the example and rerun to learn faster.
2Use readable Kotlin first; optimize later.

💡Practice: answer the questions below, then modify the example to match your answers.

1Change one value and predict the output.
2Add one edge case and handle it.
3Explain the rule in 1 sentence.

📈SEO

Keywords (topic intent):

Kotlin JVM Kotlin Inheritance

Kotlin — Complete Tutorial

Kotlin Tutorial

Kotlin HOME

Kotlin Intro

Kotlin Get Started

Kotlin Syntax

Kotlin Output

Kotlin Comments

Kotlin Variables

Kotlin Data Types

Kotlin Operators

Kotlin Strings

Kotlin Booleans

Kotlin If...Else

Kotlin When

Kotlin While Loop

Kotlin Break/Continue

Kotlin Arrays

Kotlin For Loop

Kotlin Ranges

Kotlin Functions

Kotlin Classes

Kotlin OOP

Kotlin Classes/Objects

Kotlin Constructors

Kotlin Class Functions

Kotlin Inheritance