Java First Hello World Program

Core Java | Java Tutorial

Introduction

Writing your first Java program is a simple and essential step in learning the language. The classic "Hello, World!" program is a basic program that outputs the text "Hello, World!" to the console. This guide will take you through the steps to create, compile, and run your first Java program.

Key Points:

• Creating the Program: Writing the source code.
• Compiling the Program: Converting source code to bytecode.
• Running the Program: Executing the bytecode on the Java Virtual Machine (JVM).

Steps to Create, Compile, and Run a Java Program

Step 1: Create a Java Program

Open a Text Editor or IDE

You can use any text editor such as Notepad, Sublime Text, or an Integrated Development Environment (IDE) like IntelliJ IDEA, Eclipse, or VS Code.

Write the Source Code

public class HelloWorld {
    public static void main(String[] args) {
        System.out.println("Hello, World!");
    }
}

Save the File

Save the file with a .java extension. The filename must match the class name. For this example, save the file as HelloWorld.java.

Step 2: Compile the Java Program

Open Command Prompt or Terminal

On Windows, you can open Command Prompt by searching for "cmd" in the Start menu. On macOS/Linux, open Terminal from the Applications folder or by searching for it.

Navigate to the Directory

Use the cd command to change the directory to where you saved your HelloWorld.java file.

Example command (Windows):

cd path\to\directory

Example command (macOS/Linux):

cd /path/to/directory

Compile the Program

Use the javac command to compile the Java source file:

javac HelloWorld.java

This command will create a file named HelloWorld.class in the same directory if there are no errors.

Step 3: Run the Java Program

Execute the Bytecode

Use the java command to run the compiled bytecode:

java HelloWorld

View the Output

You should see the following output in your console:

Hello, World!

Summarize Steps

 +-------------------------------------------------+
  | Step 1: Create a Java Program                   |
  +-------------------------------------------------+
  |                                                 |
  | 1. Open a Text Editor or IDE                    |
  |                                                 |
  | 2. Write the Source Code                        |
  |                                                 |
  |    public class HelloWorld {                    |
  |        public static void main(String[] args) { |
  |            System.out.println("Hello, World!"); |
  |        }                                        |
  |    }                                            |
  |                                                 |
  | 3. Save the File                                |
  |    Filename: HelloWorld.java                    |
  |                                                 |
  +-------------------------------------------------+
                      |
                      v
  +-------------------------------------------------+
  | Step 2: Compile the Java Program                |
  +-------------------------------------------------+
  |                                                 |
  | 1. Open Command Prompt or Terminal              |
  |                                                 |
  | 2. Navigate to the Directory                    |
  |    cd /path/to/directory                        |
  |                                                 |
  | 3. Compile the Program                          |
  |    javac HelloWorld.java                        |
  |                                                 |
  | 4. Output: HelloWorld.class                     |
  |                                                 |
  +-------------------------------------------------+
                      |
                      v
  +-------------------------------------------------+
  | Step 3: Run the Java Program                    |
  +-------------------------------------------------+
  |                                                 |
  | 1. Execute the Bytecode                         |
  |    java HelloWorld                              |
  |                                                 |
  | 2. View the Output                              |
  |    Hello, World!                                |
  |                                                 |
  +-------------------------------------------------+

Conclusion

Writing your first Java program is straightforward. It involves creating the source code, compiling it into bytecode, and then running it using the JVM. The "Hello, World!" program is a great way to get started with Java and understand the basics of writing, compiling, and running Java code.

Summary of Steps:

• Create the Program: Write the Java source code and save it with a .java extension.
• Compile the Program: Use the javac command to compile the source code into bytecode.
• Run the Program: Use the java command to execute the compiled bytecode.

This text-based diagram should now be aligned properly, providing a clear visual representation of the steps to create, compile, and run a Java program.

By mastering these steps, you can confidently begin your journey into Java programming and build more complex applications over time.