First Java Program: Hello World

Creating your first Java program is an essential step in learning the language. The "Hello, World!" program is a simple yet fundamental example that demonstrates the basic structure of a Java application. This guide will walk you through writing, compiling, and running your first Java program.

Writing Your First Java Program

To create a "Hello, World!" program, follow these steps:

1. Open a Text Editor: You can use any text editor, such as Notepad, TextEdit, or an Integrated Development Environment (IDE) like Eclipse or IntelliJ IDEA.
2. Write the Code: Type the following code into your text editor:

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

Explanation of the Code

• public class HelloWorld: This line declares a public class named HelloWorld. In Java, every application must have at least one class definition.
• public static void main(String[] args): This is the main method, the entry point for any Java application. The main method is always required in a standalone Java application.
• System.out.println("Hello, World!");: This line prints the text "Hello, World!" to the console. System.out is a standard output stream, and println is a method that prints a line of text.

Compiling the Program

Before running your program, you need to compile it:

1. Save the File: Save your file with the name HelloWorld.java. The filename must match the class name and be case-sensitive.
2. Open Command Prompt/Terminal: Navigate to the directory where your HelloWorld.java file is saved.
3. Compile the Program: Enter the following command to compile your program:

javac HelloWorld.java

This command uses the Java compiler (javac) to convert your Java code into bytecode, generating a HelloWorld.class file.

Running the Program

After successful compilation, run your program with the following command:

java HelloWorld

If everything is set up correctly, you should see the output:

Hello, World!

Tips and Best Practices

• Case Sensitivity: Java is case-sensitive. Ensure that you use the correct capitalization for class names, method names, and file names.
• File Naming: The filename must match the public class name exactly, including capitalization.
• Environment Setup: Ensure that Java Development Kit (JDK) is installed and configured correctly on your system. You can verify the installation by running java -version and javac -version in your command prompt or terminal.
• Use Comments: Add comments to your code to improve readability and maintainability. For example:

// This is a single-line comment

• Consistent Formatting: Follow consistent code formatting practices for better readability. Many IDEs offer automatic code formatting features.