Compile and Run Java Program

Compile and Run Java Program

Are you new to Java and trying to learn how to compile and run a simple Java program? Look no further! In this tutorial, I will walk you through the steps to compile and run your first Java program, as well as troubleshoot any issues you may encounter along the way.

Before we begin, make sure that you have the Java Development Kit (JDK) installed on your machine. If you do not have the JDK installed, you can download it from the Oracle website.

Following are the steps to compile and run a Java program:

Write the Java Program

Use a text editor to write your Java code. Save the file with a .java extension. For example, you could save it as HelloWorld.java.

Example code:

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

Open a Command Prompt or Terminal

Open a command prompt (Windows) or terminal (macOS/Linux).

Navigate to the Directory

Use the cd command to navigate to the directory where your Java file is saved. For example, if your file is saved on the desktop, you can use the command cd Desktop to navigate to the desktop directory.

Compile the Java Program

In the command prompt or terminal, enter the following command to compile the Java program:

javac HelloWorld.java

If there are no errors in your code, the Java compiler will generate a bytecode file with a .class extension. For example, if your file is HelloWorld.java, the compiler will generate HelloWorld.class.

Run the Java Program

After the compilation is successful, you can execute the Java program using the java command:

java HelloWorld

The JVM will start executing the bytecode and your program will run. Any output or results will be displayed in the command prompt or terminal.

Hence, in our example we see an output:

Hello World

It’s important to note that the javac and java commands assume that you have Java Development Kit (JDK) installed on your system and that the java and javac executables are in your system’s PATH variable. If you encounter any issues, make sure that Java is properly installed and configured on your machine.

Troubleshooting: javac or java is not recognized

If you receive an error saying that the javac or java commands are not recognized, it means that the system cannot find the executables for these commands. This can happen if the PATH environment variable is not set correctly.

You can read my other post on How to solve error “javac or java is not recognized”.

Frequently Asked Questions

How do I compile a Java program?

Compile a Java program using the javac command followed by the source code filename with the “.java” extension.

What happens during the compilation process?

During compilation, the Java source code is translated into bytecode, which is executed by the Java Virtual Machine (JVM).

How do I run a compiled Java program?

Run a Java program using the java command followed by the class name (without the “.class” extension) that contains the main method.

What is the purpose of the main method in Java?

The main method is the entry point of a Java program. It is where the program execution begins.

Can I specify command-line arguments when running a Java program?

Yes, you can pass arguments to a Java program by including them after the class name, and these arguments can be accessed within the main method using the args parameter.


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