1. Overview
Java is a general-purpose programming language that focuses on the WORA (Write Once, Run Anywhere) principle.
It runs on a JVM (Java Virtual Machine) that is in charge of abstracting the underlying OS, allowing Java programs to run almost everywhere, from application servers to mobile phones.
When learning a new language, “Hello World” is often the first program we write.
In this tutorial, we’ll learn some basic Java syntax and write a simple “Hello World” program.
2. Writing the Hello World Program
Let’s open any IDE or text editor and create a simple file called HelloWorld.java:
public class HelloWorld {
public static void main(String[] args) {
System.out.println("Hello World!");
}
}
In our example, we’ve created a Java class named HelloWorld containing a main method that writes some text to the console.
When we execute the program, Java will run the main method, printing out “Hello World!” on the console.
Now, let’s see how we can compile and execute our program.
3. Compiling and Executing the Program
In order to compile a Java program, we need to call the Java compiler from the command line:
$ javac HelloWorld.java
The compiler produces the HelloWorld.class file, which is the compiled bytecode version of our code.
Let’s run it by calling:
$ java HelloWorld
and see the result:
Hello World!
4. Conclusion
With this simple example, we created a Java class with the default main method printing out a string on the system console.
We saw how to create, compile, and execute a Java program and got familiar with a little bit of basic syntax. The Java code and commands we saw here remain the same on every OS that supports Java.