Society of Robots - Robot Forum

Software => Software => Topic started by: LeftHandRobotics on March 18, 2012, 10:50:38 AM

Title: Class not found in Hello World Project
Post by: LeftHandRobotics on March 18, 2012, 10:50:38 AM

Hello,

I recently started watching the Stanford Robotics videos, which start with sort of a "Programming 101" using Java.  I've heard great things about Java, but didn't necessarily want to learn it, since my understanding is that C++ is more common in robotics.  Be that as it may ... I'm a complete newbie to programming and even newer to Java.  I downloaded Netbeans and like the layout. My understanding is that with Netbeans I can click a "run" button and run the program automatically without using a command prompt and running the compiler (as this is how I've seen it on tutorials". When I initially went to run my HelloWorld I had the issue of my PATH not finding Javac. I had someone help me fix that ... now when I go to run the program I get this message...
"helloworld.HelloWorld class wasn't found in HelloWorld project."

My code is as follows ...

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

I'd really appreciate any help with this as I am a complete novice.  I'm not sure if this has anything to do with the whole PATH/Javac mess.  Lastly, I'm a finance guy and don't know next to nothing about software and robotics, just a hobby I've been getting into the last 4 months or so.... so please explain this to me like I am 6 ... hah ... because I spent about 5 hours last night reading and programming/debugging and am pretty upset that I can't get any program to run because I keep getting this message.

Thanks!!

Title: Re: Class not found in Hello World Project
Post by: joe61 on March 18, 2012, 07:01:11 PM

I programmed in Java for about a year a long time ago. I've done my best to stay away from it since then for reasons like this. I believe that the problem here is either in how CLASSPATH is setup, or how the jar file you're running was built.

Someone else here may be able to give you a better answer, my suggestion is to learn C instead. The only platform I can think of that you need to know Java on is Beaglebone or Android. If you're using Atmel or PIC processors, I don't think Java will do you much good.

Just my $.02

Joe

Title: Re: Class not found in Hello World Project
Post by: The Headacher on March 23, 2012, 02:59:17 AM

Using Netbeans 7 on Windows XP, I did it as follows:

Create a new Java project:
File -> New Project.
Java -> Java Application.

I named the project HelloWorld. Netbeans autogenerated a 'HelloWorld' main class.

In this class, I added the code as you had it here. It looks like this now:

Code: [Select]

package helloworld;

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

It ran just fine.

Some thoughts on what might be going on:

- missing 'package' declaration
- something else (I don't know, it's hard to tell without being able to look in your project ;) )

Good luck!

Title: Re: Class not found in Hello World Project
Post by: newInRobotics on March 23, 2012, 03:47:30 AM

Quote from: LeftHandRobotics on March 18, 2012, 10:50:38 AM

"helloworld.HelloWorld class wasn't found in HelloWorld project."

Is Your source code file named "HelloWorld.java"?