The HelloWorld Program
When learning a new programming language, the first task is normally to write a program which simply prints the words “Hello World” to your computer’s display. Once we have written, compiled, and executed the program, and verified that “Hello World” appears on the display, we have successfully run the HelloWorld program.
Section 1 - Creating and Running the HelloWorld Program
In your favorite text editor, or in your programming Integrated Development
Environment (IDE) , create a file named HelloWorld.java which contains the
following:
Listing 1 - HelloWorld.java
1 public class HelloWorld
2 {
3 public static void main(String[] args)
4 {
5 System.out.println("Hello World");
6 }
7 }
To compile and run HelloWorld.java from the command line, type the following:
javac HelloWorld.java
java HelloWorld
The Javac command runs the Java compiler which converts Java source file
HelloWorld.java into bytecode file HelloWorld.class . Java source files are text
files containing the syntax, or programming rules, of the Java programming
language. All Java source files end with the extension .java .
The Java command runs the HelloWorld.class executable in the Java Virtual
Machine (JVM). The following output is now visible on your computer display:
Hello World
Congratulations, you’ve just run your first Java program!
