First Java Program - Hello.java

∟First Java Program - Hello.java

This section provides a tutorial example on how to write, compile, and execute the first Java program, Hello.java, with OpenJDK.

With OpenJDK's JRE and JDK packages installed, we can use "javac" and "java" commands to compile and run Java programs.

"javac class_name.java" - Compiles a Java program stored a file named with the program class name.
"java -classpath . class_name" - Runs a compiled Java program. "-classpath ." specifies the current directory as the class path.

Let's try these commands with a very simple Java program. Use a text editor to enter the following Java program into a file called Hello.java:

class Hello {
  public static void main(String[] a) {
    System.out.println("Hello world!");
  }
}

Then compile this program with the "javac" command:

herong$ javac Hello.java

To execute the program, use the "java" command:

herong$ java Hello

Hello world!

Congratulations, you have successfully entered, compiled and executed your first Java program.

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