First Program IDE

This step-by-step guide walks you through creating and running your first Kotlin program using IntelliJ IDEA, the official recommended IDE for Kotlin development.

Prerequisites

• ✅ IntelliJ IDEA installed (Community or Ultimate Edition)
• ✅ JDK 8 or later installed and configured
• ✅ Basic familiarity with IDE navigation

Step 1: Launch IntelliJ IDEA

1. Open IntelliJ IDEA
2. You'll see the Welcome Screen with several options

Step 2: Create New Project

Option A: From Welcome Screen

3. Click New Project
4. The New Project wizard opens

Option B: From Menu Bar

5. Go to File → New → Project
6. The New Project wizard opens

Step 3: Configure Project Settings

Select Project Type

7. In the left sidebar, select Kotlin
8. Choose Kotlin/JVM (for console applications)
9. Click Next

Project Configuration

Name:

HelloKotlin

Location: Choose where to save the project:

C:\Users\YourName\IdeaProjects\HelloKotlin

Build System: Select one:

• ✅ Gradle (Kotlin DSL) - Recommended for larger projects
• ✅ Maven - Alternative build tool
• ✅ IntelliJ - Simple, no build tool (good for learning)

JDK: Select your installed JDK:

• ✅ Choose from dropdown
• ✅ Or click Download JDK to install automatically

Example configuration:

Name: HelloKotlin
Location: C:\Users\YourName\IdeaProjects\HelloKotlin
Build System: IntelliJ
JDK: 17 (corretto-17)

Click Create

Step 4: Understanding Project Structure

IntelliJ creates this structure:

HelloKotlin/
├── .idea/              # IDE configuration
├── out/                # Compiled output
├── src/                # Source code
│   └── Main.kt         # Your Kotlin files go here
└── HelloKotlin.iml   # Project module file

Step 5: Create Kotlin File

Method 1: Quick Creation

1. Right-click on src folder in Project view (left sidebar)
2. Select New → Kotlin Class/File
3. In the dialog:

• ✅ Choose File (not Class)
• ✅ Enter name: HelloWorld
• ✅ Press Enter

Method 2: Using Menu

1. Click on src folder
2. Go to File → New → Kotlin Class/File
3. Follow same steps as Method 1

Result

A new file HelloWorld.kt is created and opened in the editor.

Step 6: Write Your First Kotlin Code

In HelloWorld.kt, type:

fun main() {
    println("Hello, Kotlin!")
    println("Welcome to IntelliJ IDEA!")
}

Code Explanation

• ✅ fun main: Entry point function
• ✅ println: Prints text with newline
• ✅ Strings in double quotes
• ✅ No semicolons needed

IntelliJ Features While Typing

Auto-completion:

• ✅ Start typing fun - IntelliJ suggests fun
• ✅ Press Tab to complete

Auto-closing:

• ✅ Type ( - IntelliJ adds ) automatically
• ✅ Type { - IntelliJ adds } automatically

Syntax highlighting:

• ✅ Keywords appear in color
• ✅ Strings appear in different color
• ✅ Errors underlined in red

Step 7: Run the Program

Method 1: Green Play Button

1. Look for the green ▶ (play) icon next to fun main
2. Click the play button
3. Select Run 'HelloWorldKt'

Method 2: Context Menu

4. Right-click anywhere in the editor
5. Select Run 'HelloWorldKt'

Method 3: Keyboard Shortcut

Windows/Linux:

Ctrl + Shift + F10

macOS:

Control + Shift + R

Method 4: Top Menu Bar

1. Click Run in menu bar
2. Select Run 'HelloWorldKt'

Step 8: View Output

Run Tool Window

The Run window opens at the bottom showing:

Hello, Kotlin!
Welcome to IntelliJ IDEA!

Process finished with exit code 0

Understanding the Output

• ✅ First two lines: Your program output
• ✅ exit code 0: Program ran successfully
• ✅ exit code != 0: Program had an error

Step 9: Modify and Re-run

Let's make the program interactive:

fun main() {
    println("=" .repeat(40))
    println("Welcome to Kotlin Programming!")
    println("=" .repeat(40))
    
    val language = "Kotlin"
    val year = 2024
    
    println("\nLanguage: $language")
    println("Year: $year")
    println("$language is awesome!")
}

Run again to see the new output:

========================================
Welcome to Kotlin Programming!
========================================

Language: Kotlin
Year: 2024
Kotlin is awesome!

Process finished with exit code 0

Useful IntelliJ IDEA Features

1. Code Formatting

Auto-format your code:

Windows/Linux: Ctrl + Alt + L

macOS: Cmd + Option + L

2. Code Completion

Type pri and press Ctrl + Space to see suggestions:

• ✅ println
• ✅ print
• ✅ private

Select with arrow keys and press Enter.

3. Quick Documentation

Hover over println and press Ctrl + Q (Windows/Linux) or F1 (macOS) to see documentation.

4. Rename Refactoring

To rename a variable:

1. Right-click variable name
2. Select Refactor → Rename
3. Or press Shift + F6
4. Type new name
5. Press Enter (renames everywhere)

5. Run Configuration

After first run, you can:

• ✅ Click play button in toolbar (top-right)
• ✅ Use shortcut Shift + F10 (Windows/Linux) or Control + R (macOS)

Common Issues and Solutions

Issue 1: No Run Button Visible

Cause: Kotlin plugin not enabled

Solution:

1. File → Settings → Plugins
2. Search "Kotlin"
3. Enable if disabled
4. Restart IDE

Issue 2: Cannot Find JDK

Cause: JDK not configured

Solution:

1. File → Project Structure (Ctrl + Alt + Shift + S)
2. Project Settings → Project
3. Project SDK: Select or add JDK
4. Click OK

Issue 3: Red Underline Under Code

Cause: Syntax error or missing import

Solution:

1. Hover over red text to see error
2. Press Alt + Enter for quick fixes
3. Select suggested fix

Issue 4: Program Doesn't Run

Cause: Wrong file selected or no main function

Solution:

1. Ensure file contains fun main
2. Right-click on correct file
3. Select Run

Practice Exercises

Exercise 1: Personal Info

Create a program that prints:

Name: [Your Name]
Age: [Your Age]
Location: [Your City]

Exercise 2: Simple Calculator

fun main() {
    val a = 10
    val b = 5
    
    println("$a + $b = ${a + b}")
    println("$a - $b = ${a - b}")
    println("$a * $b = ${a * b}")
    println("$a / $b = ${a / b}")
}

Exercise 3: Multiple Lines

Print a simple pattern:

fun main() {
    println("*****")
    println("*   *")
    println("*   *")
    println("*****")
}

Keyboard Shortcuts Cheat Sheet

Next Steps

• ✅ Experiment with different print statements
• ✅ Try using variables (val and var)
• ✅ Learn about Kotlin data types
• ✅ Explore IntelliJ debugging features
• ✅ Create more complex programs

Tips for Beginners

1. Use code completion: Saves time and reduces typos
2. Read error messages: They tell you exactly what's wrong
3. Experiment freely: Can't break anything, easy to undo
4. Use shortcuts: Much faster than mouse clicking
5. Save often: Ctrl + S (though IntelliJ auto-saves)

Congratulations! You've created and run your first Kotlin program in IntelliJ IDEA. Keep practicing and exploring Kotlin's features!