Lesson 2: Hello World#

In this lesson, you’ll write your first Java program in Neovim and learn the basics of editing with Vim motions.

Learning Objectives#

By the end of this lesson, you’ll be able to:

• Write a simple Java program
• Understand Vim modes (Normal, Insert, Visual)
• Use basic editing commands
• Save and run your program

Vim Modes Quick Reference#

Neovim has different modes for different tasks:

Tip: You’ll spend most time in Normal mode, briefly entering Insert mode to type.

Creating Hello World#

Open your project:

cd ~/java-projects/maven-demo
nvim .

Create or open Main.java:

1. Press <Space>ne to open file explorer
2. Navigate to src/main/java/com/example/
3. Press a to create new file
4. Type: Main.java
5. Press Enter

Writing the Code#

Now you’re in Insert mode (if not, press i). Type the following:

package com.example;

public class Main {
    public static void main(String[] args) {
        System.out.println("Hello from Neovim!");
    }
}

Basic Vim Editing#

Entering Insert Mode:

• i - Insert before cursor
• a - Insert after cursor
• o - Open new line below
• O - Open new line above

Leaving Insert Mode:

• Esc - Return to Normal mode

Moving Around (Normal Mode):

• h, j, k, l - Left, Down, Up, Right
• w - Next word
• b - Previous word
• 0 - Start of line
• $ - End of line
• gg - Top of file
• G - Bottom of file

Deleting (Normal Mode):

• x - Delete character
• dd - Delete line
• dw - Delete word
• d$ - Delete to end of line

Undo/Redo:

• u - Undo
• Ctrl-r - Redo

Saving Your File#

In Normal mode (press Esc first):

:w

Or use the leader key shortcut:

<Space>w

Running Your Program#

Option 1: Using Maven#

Open a terminal (you can split Neovim or use a separate terminal):

mvn compile
mvn exec:java -Dexec.mainClass="com.example.Main"

Option 2: Using Gradle#

gradle build
gradle run

Option 3: Direct Compilation (for simple projects)#

# Compile
javac src/main/java/com/example/Main.java

# Run
java -cp src/main/java com.example.Main

Option 4: Using Neovim Terminal#

You can run commands without leaving Neovim:

1. Press <C-7> (Ctrl+7) to toggle the terminal
2. Run your Maven/Gradle commands
3. Press <C-7> again to toggle back, or Ctrl-\ then Ctrl-n to exit terminal mode
4. Type exit to close the terminal

Editing Practice#

Let’s practice editing your Hello World program:

Exercise 1: Add More Output#

1. Move to the line with System.out.println
2. Press o to open a new line below
3. Type: System.out.println("Welcome to Java development with Neovim!");
4. Press Esc to return to Normal mode
5. Save with :w

Exercise 2: Change the Message#

1. Move cursor to “Hello” in the string
2. Press ciw (change inner word)
3. Type: Greetings
4. Press Esc
5. Save with :w

Exercise 3: Duplicate a Line#

1. Move to any System.out.println line
2. Press yy to yank (copy) the line
3. Press p to paste below
4. Edit the new line as needed
5. Save with :w

Common Vim Commands Summary#

Troubleshooting#

LSP Not Working?#

Check if jdtls is running:

:LspInfo

You should see jdtls listed as attached.

Syntax Highlighting Issues?#

Make sure Treesitter is installed:

:checkhealth nvim-treesitter

Build Errors?#

Check your Java version:

java -version
javac -version

Make sure your pom.xml or build.gradle specifies the correct Java version.

Tips for Vim Beginners#

1. Stay in Normal mode - Don’t keep Insert mode on all the time
2. Use motions - w, b, e are faster than arrow keys
3. Practice hjkl - It feels awkward at first but becomes natural
4. Learn incrementally - Master a few commands, then add more
5. Run :Tutor - Neovim’s built-in tutorial is excellent

Practice Exercise#

Create a new class called Calculator.java:

package com.example;

public class Calculator {
    public int add(int a, int b) {
        return a + b;
    }

    public static void main(String[] args) {
        Calculator calc = new Calculator();
        int result = calc.add(5, 3);
        System.out.println("5 + 3 = " + result);
    }
}

Use only Vim motions to:

1. Create the file
2. Write the code
3. Save it
4. Run it

What’s Next?#

In Lesson 3: Code Completion, you’ll learn to use intelligent auto-completion to code faster.