Chapter 2 — Setting Up Java

Chapter 02 — Phase 1: Fundamentals

Setting Up Java

Install the JDK, configure your environment, set up a professional IDE, and run your first Java program three different ways. No prior setup experience needed — every step is covered.

~30 min read

Practical Setup

All OS Covered

12 Practice Problems

📦

2.1 — InstallInstalling the JDK

The JDK (Java Development Kit) is the foundation. Without it, you cannot compile or run Java programs. It includes the compiler (javac), the runtime (JVM), and all core Java libraries.

Which JDK to Install?

Always choose an LTS (Long-Term Support) version — it is stable and supported for years. Recommended: JDK 17 or JDK 21. Avoid odd-numbered versions like 19 or 23 — they are short-term releases.

Step 1 — Download

Two reliable, free sources:

Source	URL	Notes
Eclipse Temurin (Recommended)	`adoptium.net`	Free, open-source, community-backed. Best for students.
Oracle JDK	`oracle.com/java`	Official Oracle release. Free for personal/dev use.
Amazon Corretto	`aws.amazon.com/corretto`	Free, enterprise-grade, maintained by Amazon.

On the download page: select your operating system (Windows/Mac/Linux), your architecture (x64 for most PCs, aarch64 for Apple M1/M2), and download the installer (.msi for Windows, .pkg for Mac, .deb or .rpm for Linux).

Step 2 — Set Environment Variables

After installing, the system needs to know where Java is installed so that java and javac commands work from any folder in the terminal.

Windows — Setting JAVA_HOME and PATH:

Right-click This PC → Properties → Advanced system settings
Click Environment Variables button at the bottom
Under System variables, click New:
Variable name: JAVA_HOME
Variable value: C:\Program Files\Java\jdk-17 (your actual install path)
Find the Path variable → click Edit → click New → type: %JAVA_HOME%\bin
Click OK on all dialogs. Open a new Command Prompt (important — old ones won't see the change).

Windows CMD — Verify

C:\> java --version
openjdk 17.0.9 2023-10-17

C:\> javac --version
javac 17.0.9

C:\> echo %JAVA_HOME%
C:\Program Files\Java\jdk-17

macOS — Using .pkg installer (easiest):

Run the downloaded .pkg file — it installs automatically to /Library/Java/JavaVirtualMachines/
Open Terminal and add to your shell profile. For Zsh (default on modern Mac), edit ~/.zshrc:

macOS Terminal — Setup

# Add to ~/.zshrc (open with: nano ~/.zshrc)
export JAVA_HOME=$(/usr/libexec/java_home -v 17)
export PATH=$JAVA_HOME/bin:$PATH

# Apply changes:
source ~/.zshrc

# Verify:
java --version
javac --version

Linux (Ubuntu/Debian) — Using apt:

Linux Terminal — Install & Verify

# Update packages and install JDK 17:
sudo apt update
sudo apt install openjdk-17-jdk

# Verify installation:
java --version
javac --version

# If multiple Java versions exist, choose default:
sudo update-alternatives --config java

# Set JAVA_HOME (add to ~/.bashrc):
export JAVA_HOME=/usr/lib/jvm/java-17-openjdk-amd64
export PATH=$JAVA_HOME/bin:$PATH
source ~/.bashrc

Step 3 — Verify Installation

Open a brand new terminal window and run both commands. Both must show version numbers:

Terminal — Both Commands Must Work

$ java --version
openjdk 17.0.9 2023-10-17
OpenJDK Runtime Environment Temurin-17.0.9+9

$ javac --version
javac 17.0.9

If You See Version Numbers — You're Done!

Both java and javac working means JDK is installed and your PATH is correct. You are ready to compile and run Java programs.

If Commands Are Not Recognized

Windows: Did you open a NEW Command Prompt after setting PATH? Old ones don't see new variables.
All OS: Check that JAVA_HOME points to the correct folder where JDK was installed.
All OS: Make sure you added %JAVA_HOME%\bin (Windows) or $JAVA_HOME/bin (Mac/Linux) — the \bin part is essential.
Mac: Did you run source ~/.zshrc after editing the file?

🖥️

2.2 — ToolsChoosing Your IDE

An IDE (Integrated Development Environment) is a smart code editor with features like autocomplete, error highlighting, and one-click running. You can write Java in Notepad — but a good IDE makes you 10x more productive.

IDE	Best For	Pros	Cons	Cost
IntelliJ IDEA Community	Professional & students	Best Java intelligence, smart autocomplete, refactoring, built-in debugger	Higher RAM usage (~500MB+)	Free
VS Code	Lightweight daily use	Fast, free, great extensions ecosystem, low RAM	Needs extensions, not Java-native	Free
Eclipse	University & enterprise	Widely used in academia, powerful features	Older UI, can feel slow	Free
BlueJ	Complete beginners	Designed for learning OOP, shows object diagrams	Not used in real-world work	Free
Replit / JDoodle	Quick experiments	No installation, runs in browser	Limited features, needs internet	Free

Recommendation for CSE Students

Use IntelliJ IDEA Community Edition for daily work and assignments — it has the best Java support and will be familiar when you enter the industry. Use VS Code when on a low-RAM machine. Know how to run from the terminal too — university lab exams may not have IDEs.

IntelliJ IDEA — Complete Setup

Download

Go to jetbrains.com/idea → Download Community Edition (free). Run the installer, accept defaults.

Create New Project

Open IntelliJ → New Project → Select Java on the left → Choose your JDK from the dropdown → Name your project (e.g., JavaCourse) → Click Create.

Create a Java Class

In the Project panel (left), right-click the src folder → New → Java Class → Type HelloWorld → Press Enter.

Write Your Code

The editor opens. Type psvm and press Tab — IntelliJ auto-expands it to the full main method! Type sout + Tab for System.out.println().

Run

Click the green ▶ Play button next to the main method, or press Shift+F10. Output appears in the Run panel at the bottom.

IntelliJ Live Templates — Speed Up Typing

Type This	Press	Expands To
`psvm`	Tab	`public static void main(String[] args) { }`
`sout`	Tab	`System.out.println();`
`soutv`	Tab	`System.out.println("varName = " + varName);`
`fori`	Tab	Full `for(int i=0; i<n; i++)` loop
`iter`	Tab	Enhanced for-each loop

VS Code — Java Setup

Install VS Code

Download from code.visualstudio.com. Free, fast, works on all OS.

Install Java Extension Pack

Open VS Code → click the Extensions icon (Ctrl+Shift+X) → search "Extension Pack for Java" by Microsoft → Install. This adds: language support, debugger, test runner, and Maven support.

Open a Folder & Create File

File → Open Folder → create a new folder for your project. Create a new file named HelloWorld.java. VS Code will detect it as Java automatically.

Run

A "Run Java" link appears above the main method. Click it. Output appears in the Terminal panel below.

▶️

2.3 — ExecutionRunning Java — Three Ways

You should know all three methods. University lab exams may only have a terminal. Job interviews may ask you to compile from command line.

Way 1 — Terminal / Command Prompt (Master This First)

Terminal — Full Workflow

# Step 1: Navigate to the folder containing your .java file
cd Desktop/JavaProjects

# Step 2: List files to confirm your .java file is there
ls          # Mac/Linux
dir         # Windows

# Step 3: Compile — creates HelloWorld.class in the same folder
javac HelloWorld.java

# Step 4: Run — use class name, NOT filename
java HelloWorld

# Output:
Hello, World!

Essential Terminal Commands

Command	Windows	Mac / Linux
Go into folder	`cd FolderName`	`cd FolderName`
Go up one level	`cd ..`	`cd ..`
List files	`dir`	`ls`
Clear screen	`cls`	`clear`
Show current path	`cd`	`pwd`

Way 2 — IntelliJ IDEA (Fastest for Development)

Once set up (see Section 2.2), simply press Shift+F10 or click the green play button. IntelliJ handles compilation and running automatically. You can see output, errors, and debug all in one window.

Key IntelliJ Shortcuts

Shortcut	Action
`Shift+F10`	Run current program
`Shift+F9`	Debug current program
`Ctrl+Z`	Undo
`Ctrl+/`	Toggle comment on line
`Ctrl+D`	Duplicate current line
`Alt+Enter`	Quick fix (fix errors automatically)
`Ctrl+Shift+F10`	Run the file in the editor

Way 3 — Online Compiler (No Installation Needed)

Useful when you're on a different computer or want to test quickly. Just paste code and run.

Site	URL	Best Feature
JDoodle	`jdoodle.com`	Simple, fast, supports multiple Java versions
Replit	`replit.com`	Full project support, shareable links
OnlineGDB	`onlinegdb.com`	Has debugger, good for tracing code
Programiz	`programiz.com/java-programming/online-compiler`	Clean UI, good for beginners

📁

2.4 — OrganisationRecommended Project Structure

Keeping your files organised from day one is a professional habit. Here's a structure that works for university coursework:

JavaCourse/ ← Root project folder ├── Chapter01/ │ ├── HelloWorld.java │ └── HelloWorld.class ← created by javac ├── Chapter02/ │ └── SetupTest.java ├── Chapter04/ │ ├── Variables.java │ └── DataTypes.java ├── OOP/ │ ├── Student.java │ └── BankAccount.java └── Practice/ ├── Easy/ └── Medium/ Rule: ONE public class per .java file. File name must match public class name exactly.

IntelliJ Project vs Simple Folder

In IntelliJ, code goes inside the src/ folder of your project. The compiled .class files go to out/production/ automatically. You never need to run javac manually in IntelliJ — it compiles in the background as you type.

🚨

2.5 — TroubleshootComplete Error Guide

Every beginner hits these errors. Here they are with exact causes and fixes:

🚨 Error Reference Table

Error Message	Cause	Fix
'java' is not recognized	PATH not set / terminal not restarted	Set JAVA_HOME + PATH, open NEW terminal
'javac' is not recognized	JRE installed instead of JDK, or PATH missing	Install JDK (not JRE), add bin to PATH
error: class X is public, should be in file X.java	Filename doesn't match class name	Rename file to exactly match class name (case-sensitive)
error: ';' expected	Missing semicolon at end of statement	Add `;` at the line shown in error
error: reached end of file while parsing	Missing closing brace `}`	Count opening vs closing braces — add the missing one
Could not find or load main class X	Wrong class name in run command, or in wrong folder	Use `java ClassName` (no .class). Run from folder containing .class file
Main method not found in class X	main method missing or wrong signature	Ensure exact signature: `public static void main(String[] args)`
error: cannot find symbol	Variable/method not declared, or typo	Check spelling, ensure variable is declared before use

How to Read Java Error Messages

Java errors show: FileName.java:LineNumber: error: description

Sample Error

HelloWorld.java:5: error: ';' expected
        System.out.println("Hello")
                                   ^
1 error

HelloWorld.java — which file has the error
5 — which line number to look at
error: ';' expected — what Java expected but didn't find
^ — caret points to the exact position of the problem

Always fix errors from top to bottom — one error can cascade into many. Fix the first one and recompile before worrying about the others.

✅

2.6 — VerifyComplete Setup Checklist

Tick every item to confirm your environment is fully working:

java --version shows a version number in the terminal

javac --version shows a version number in the terminal

JAVA_HOME environment variable is set correctly

You can create and save a .java file

You can compile HelloWorld.java using javac in terminal with no errors

You can run HelloWorld using java HelloWorld and see output

IDE (IntelliJ or VS Code) is installed and can run Java programs

You can use an online compiler as a backup

📝

2.7 — ExamExam Preparation

2 Marks — Short Answer

Q: What is JAVA_HOME and why must it be set?

Answer: JAVA_HOME is an environment variable that stores the installation path of the JDK on the system. It must be set so that the operating system and other tools (like build tools Maven and Gradle) can locate the JDK directory. The PATH variable is then set to include %JAVA_HOME%\bin (Windows) so that java and javac commands can be executed from any directory in the terminal.

3 Marks — Explain

Q: What is the difference between compiling and running a Java program? Write the exact commands used.

Answer: Compiling is the process of translating Java source code (.java file) into bytecode (.class file) using the Java compiler. Command: javac HelloWorld.java — this creates HelloWorld.class. Running is the process of launching the JVM to execute the compiled bytecode. Command: java HelloWorld — note there is no file extension; Java takes the class name, not the filename. The JVM then loads the .class file, finds the main method, and executes it.

MCQs

Q1.Which command compiles a Java source file named Test.java?

Ajava Test.java

Bjavac Test.java

Cjava Test

Dcompile Test.java

✓ javac is the Java compiler command. javac Test.java compiles the source file and produces Test.class. The java command is for running, not compiling.

Q2.After compiling HelloWorld.java, which file is created?

AHelloWorld.exe

BHelloWorld.class

CHelloWorld.jar

DHelloWorld.bin

✓ Compilation with javac produces a .class file containing bytecode. This is NOT machine code — it's an intermediate format the JVM can run on any platform.

Q3.What does the IDE shortcut psvm expand to in IntelliJ?

ASystem.out.println();

Bpublic static void main(String[] args) { }

CA for loop template

DA class template

✓ psvm is a Live Template in IntelliJ that expands to the full main method signature. Type it and press Tab. Similarly, sout + Tab expands to System.out.println();.

Q4.You see: 'javac' is not recognized as an internal or external command. Most likely cause?

AJava code has a syntax error

BThe .java file doesn't exist

CJDK bin directory is not in the PATH environment variable

DThe program has a runtime error

✓ This error means the OS cannot find the javac executable. Either the JDK is not installed, the bin folder was not added to PATH, or the terminal wasn't restarted after setting PATH.

Q5.Which of the following is the CORRECT command to run a compiled Java class named MyApp?

Ajava MyApp.java

Bjavac MyApp

Cjava MyApp

Djava MyApp.class

✓ java MyApp is correct — no extension. The java launcher takes the class name. java MyApp.java would try to find a class literally named "MyApp.java". java MyApp.class would try to find a class named "MyApp.class".

Memory Tips — Chapter 2

javac vs java: "javac = compile (C for Compile). java = run."
No extension when running: java HelloWorld not java HelloWorld.class — you give the class NAME, not the filename.
Fix errors top to bottom: One error often causes 10 more. Fix the first, recompile, repeat.
New terminal after PATH change: Environment variables are loaded when the terminal starts — old terminals don't see new values.
psvm + Tab: The fastest way to type the main method in IntelliJ. sout + Tab for println.

Quick Revision — Chapter 2

Download JDK from adoptium.net or oracle.com. Choose LTS version (17 or 21).

Set JAVA_HOME to JDK install path. Add $JAVA_HOME/bin to PATH. Open NEW terminal to apply.

Verify: java --version and javac --version must both show version numbers.

Compile: javac FileName.java → creates FileName.class. Run: java ClassName (no extension).

IntelliJ: best IDE for Java. psvm+Tab → main method. sout+Tab → println. Shift+F10 → run.

VS Code: install "Extension Pack for Java" by Microsoft for Java support.

Error "not recognized" → PATH not set. Error "class X should be in file X.java" → filename mismatch.

Fix errors top to bottom. Read: filename:lineNumber:description. ^ points to the exact problem location.

💪

2.8 — PracticePractice Problems

Easy

P2.1

Verify Setup

Run both java --version and javac --version in your terminal. Take note of the version numbers. If either fails, fix it before continuing.

EasyPractical

P2.2

Terminal Workflow

Create HelloWorld.java using only a plain text editor (Notepad or gedit — no IDE). Compile and run it entirely from the terminal. Confirm output.

EasyPractical

P2.3

IntelliJ First Program

Create a new IntelliJ project. Use psvm and sout shortcuts to write a program that prints your name. Run with Shift+F10.

Easy

P2.4

Error Reproduction

Deliberately rename your .java file so it doesn't match the class name. What exact error do you get? Fix it. Document what you learned.

EasyDebug

P2.5

Three Ways Challenge

Run the same HelloWorld program all three ways: terminal, IDE, and an online compiler (jdoodle.com). Screenshot or note the output from each.

EasyPractical

Medium

P2.6

Project Folder Structure

Create the folder structure shown in Section 2.4 on your computer. Place a working Java file in Chapter01, Chapter02, and Practice/Easy folders. Compile and run each from the correct directory.

Medium

P2.7

Error Message Collection

Intentionally create each of these errors: missing semicolon, missing brace, wrong capitalization, wrong run command. Document the exact error message, line number, and fix for each.

MediumDebug

P2.8

Multiple Files

Create three separate Java files in the same folder: First.java, Second.java, Third.java — each printing a different message. Compile all three with one command: javac *.java. Then run each.

Medium

P2.9

IDE vs Terminal Compare

Write a program with a deliberate error (e.g., missing semicolon). Compare how IntelliJ highlights it vs how the terminal shows it. Which gives more helpful feedback?

Medium

Hard

P2.10

JAVA_HOME Deep Dive

In a terminal, print the full contents of your JAVA_HOME directory (ls $JAVA_HOME/bin on Mac/Linux, dir %JAVA_HOME%\bin on Windows). Identify at least 8 tools listed and look up what each one does.

Hard

P2.11

Javadoc Generation

Write a class with a /** */ Javadoc comment above the class declaration. Then run javadoc ClassName.java in the terminal. Open the generated HTML file. This is how Java API documentation is made.

Hard

P2.12

Setup Documentation

Write a complete Java program that, when run, prints step-by-step Java installation instructions for a friend using your operating system. Include all commands they'd need to type.

Hard

Chapter 2 Challenge

True setup mastery means you can recover from anything.

Unset your PATH temporarily (or open a fresh shell without Java in PATH) and try running Java. Reproduce the "not recognized" error, then fix it from scratch.
Without any IDE: write, compile, and run a program that prints a 5-line formatted table using only a plain text editor and terminal commands.
Find out: what Java version is installed on your university lab computers? Is it JDK or JRE? How can you tell the difference from the command line?

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Chapter 1: Intro to Programming

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Chapter 3: Java Syntax Basics