Class will not execute

Jemdt · 06-19-2012, 08:25 PM

Hi, I'm fairly new to problem, and I've instantly come across the problem which appears that every newbie seems to come across.

I'm working off a book, on to which a very simple system.out.println code was given out (below):

Code:

public class HelloWorld {

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

}

The .java file compiles without any errors at all and a HelloWorld.class file is created. However, whenever I type in either:

Code:

java C:\MYLOCATION\HelloWorld

OR

Code:

java -cp . C:\MYLOCATION\Helloworld

I get the same error:

"Error: Could not find or load the main class HelloWorld"

The class runs fine on Eclipse, but I'd like to know how to do it correctly without the use of an IDE.

Thanks,

James

jordandap · 06-19-2012, 10:09 PM

just a small error qouted the error and put the correct statment on top you just had the [] in the wrong place

Code:

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

}

Fou-Lu · 06-19-2012, 10:45 PM

No, that's not correct. Main actually accepts several different signatures. Offhand these will all work (assuming at least 5 since it uses vargs):

PHP Code:


			
public static void main(String[] argv);
public static void main(String argv[]);
public static void main(String... argv);

You can actually just give it a string as well.

For the OP, change your directory to the path to execute. When you issue path/class it expects that as the package of the class itself from the -cp directives set. This has no package, so you want to simply use java HelloWorld from the C:\MyLocation directory.

Edit:
BTW, the most common and best suited signature is public static void main(String[] argv) as it clearly identifies the String as the array.

Jemdt · 06-20-2012, 05:42 PM

Quote:

Originally Posted by Fou-Lu

You can actually just give it a string as well.

For the OP, change your directory to the path to execute. When you issue path/class it expects that as the package of the class itself from the -cp directives set. This has no package, so you want to simply use java HelloWorld from the C:\MyLocation directory.

Sorry, I'm not quite sure what you mean. Could you possibly give an example? Thanks.

Fou-Lu · 06-20-2012, 06:05 PM

Code:

> cd /d C:\MyLocation
> java HelloWorld

Try that.

michaelh73 · 06-22-2012, 06:06 AM

Quote:

Originally Posted by Jemdt

Code:

java -cp . C:\MYLOCATION\Helloworld

I'm not sure if you did this while you were trying to run it, but java is case sensitive so your class name is HelloWorld, and not Helloworld like you've shown above.

But changing directories like Fou-Lu said above will make your life easier, and also help keep you from making tiny errors