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Here's the prototypical first Java application -- HelloWorld.java:

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

That's about as small as a Java application gets!

Compile it:

javac HelloWorld.java

which produces a HelloWorld.class file.

Then execute it:

java HelloWorld

Note: We're executing the class, not the file!

It should output:

Hello World!!

followed by a newline.

Note: In the real world, the actual command line contents are more complex than this.   IDEs simplify things by doing all the nitty-gritty nasty stuff under the covers.

This page was last modified on 02 October, 2007