Command line execution in Java - Mini Project: Build & Apply

Command Line Execution in Java

📖 Scenario: You are creating a simple Java program that prints a greeting message. You will write the code step-by-step and then run it from the command line.

🎯 Goal: Build a Java program named HelloWorld that prints Hello, Java! to the console. Learn how to write the code, compile it, and run it using the command line.

📋 What You'll Learn

Create a Java class named HelloWorld

Add a main method to the class

Print the exact text Hello, Java! to the console

Compile the Java program using javac HelloWorld.java

Run the compiled program using java HelloWorld

💡 Why This Matters

🌍 Real World

Java programs are often run from the command line during development and deployment.

💼 Career

Knowing how to compile and run Java code from the command line is essential for Java developers and software engineers.

1

Create the HelloWorld class

Write a public Java class named HelloWorld. Do not add anything else yet.

Java

public class HelloWorld {
    // Your code here
}

Need a hint?

Start by typing public class HelloWorld { } exactly.

2

Add the main method

Inside the HelloWorld class, add a public static void main method with the exact signature public static void main(String[] args).

Java

public class HelloWorld {
    public static void main(String[] args) {
        // Your code here
    }
}

Need a hint?

Remember the exact method signature: public static void main(String[] args).

3

Print the greeting message

Inside the main method, write a line to print Hello, Java! exactly using System.out.println.

Java

public class HelloWorld {
    public static void main(String[] args) {
        // Your code here
    }
}

Need a hint?

Use System.out.println("Hello, Java!"); to print the message.

4

Run the program from the command line

After saving your file as HelloWorld.java, compile it by running javac HelloWorld.java in the command line. Then run the program with java HelloWorld. The output should be exactly Hello, Java!.

Java

// Save and compile your program using javac, then run it using java
// Your code here

Need a hint?

Use your terminal or command prompt to run these commands:
javac HelloWorld.java
java HelloWorld