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JWrapper - cannot find main class

I'm trying to evaluate JWrapper for enterprise purchase, but the app it builds cannot find its main class. I'm using the free version GUI app. It claims to be successfully building my app. The initial launch java app (the Wrapper app) seems to fine, that closes and launches another java process, presumably my code, but then crash. Three Wrapper log files are created, the last being named for my app, and the error I see in that log is "Class not found" for my main class. I have entered the main class name correctly. I have entered the main class name in every possible permutation of the main class name I could think of. As far as I can tell, I've followed all the (rather sparse) instructions on the JWrapper website exactly. Can anyone help me? There's probably some simple answer but I've been struggling with this for days. JWrapper seems like nice software, in theory, but I'm not paying $500/year for something I can't get to work! There seems to be no help available. Anyone?

If you are able to launch the class from the command line using your JAR file then JWrapper will also be able to run it. You may want to check that you are using dots as separators to the class file rather than slashes, in keeping with the Java ClassLoader convention, for example:
com.mycompany.MyClass
rather than
com/mycompany/MyClass

How do I make a java .exe to allow user to interact as I would in the eclipse command window?

I wrote a simple java code that would take simple inputs from the user in the command window (of eclipse for me) using nextInt() and nextLine(). However, I realized that others need JRE (I believe?) on their computer to run the executable jar file made. So I was wondering if there is a way to get around that by making the app produce a window that is like the command window to have the same interaction as the command window in eclipse.
So, if I were to run the .jar or .exe then a simple window would pop up that acts like the console of eclipse displaying lines from System.out.println() and etc.

To run a java program you need the jre. There is no way around that.
If you need the console, nothing is stopping you from running the java program from the windows command line, which will do exactly what you ask for.
You still need the JRE.
Unfortunately, when starting to learn Java with Eclipse, many people miss the opportunity to at least start to understand how to do the same from the command line, which is, if you ask me, good to know.

For programs written in Java, they are compiled as a jar file, like you mentioned, and how these compiled versions of your source code differs from many other programming languages is that they do not contain the assembly/machine code like for example a compiled C program would have. They are instead compiled as bytecode. Which is special code for execution by a Java Virtual Machine. Here is a good Wikipedia reference: link
To answer your question, yes, others need a JRE (Java Runtime Environment) and this can be either:
Installed by themselves (this is what you mentioned)
Packaged together with your java app, to provide a download-and-click experience.
For option 1, assuming they already have it installed, they can simply run it by executing the jar file with javaw, more information on that is in this previously answered SO question
For option 2, the process is fairly lengthy and I'll point you to the official docs to refer to: self contained executables and Deploying java apps
If you have a more complex project with third party libraries and what not, look at this SO question
In the past, I've also found launch4j, a cross-platform wrapper to be very useful, it automates the process of going from jar to an executable (made a simple game that using Swing, simple and ugly thing it was), but the user still needs a JRE, nonetheless. :)
Hope this helps!

Works fine in NetBeans, Have some errors when built

I am in a very very upset situation. My program worked 100% fine when it is in netbeans, but when I build it it has some issues. That is, in my program, there is an one interface and 10 implementation classes. Program calls correct correct implementation class based on how the user save the file (eg: if user save it as game.yellow, it will call "YellowImpl.java", if saved as game.red, then "RedImpl.java" likewise).
But when it is built, it is calling everything fine, instead YellowImpl!! Which means, if the user saves it as game.red, it will call "RedImpl" correctly and same to all other implementations instead YellowImpl. When the user save the file as game.yellow, the program do nothing!!! But this is not happening when it is inside the netbeans! I tried clean and build too, still not good! What is causing this ? Please help!
However, I am unable to provide the code, because it has lot of codings
PS: I am using some libs too

It's difficult to understand exactly what issue you are having with your explaination and no code. However I assume you are having issue with implementation naming conventions.
Perhaps the below link can help.
Java Interfaces/Implementation naming convention

I am agree with #Rhys: it is hard to understand what happens in your application. Just let me give you an advice: do not think (even for 1 second) that there is a bug in java compiler, JVM etc. It is definitely your bug.
How to find it? I suggest you to use remote debugging.
Run your application outside IDE (NetBeans in your case) with enabled remote debugger, connect to it with net beans and debug your application. I believe you will fined the problem within minutes.
How to enable remote debugging? Add the following long string to your java execution command line:
-Xdebug -Xrunjdwp:transport=dt_socket,address=8000,server=y,suspend=n
If something happens in very beginning of your program execution use suspend=y.
Now connect to this application from NetBeans. It is simple, just configure it to port 8000 according to the configuration of your application.
That's it. Good luck.

Thanks a lot for the replies guys. However, I managed to find the issue. That was a simple, capital case!! I have a package called "kolor" and all the implementations are inside that. In my "YelloImpl" class, I have mentioned the package as "Kolor" (Note that "K" is capital). It was fine in netbeans, but outside it wasn't. After clearing this out, everything went fine. Thanks all for the replies again.

How to execute console or GUI input as if it was actual Java code?

I want to be able to input java commands/code to execute during run-time (during the execution of a "persistent" program) in the same way, or as close as possible, to the same code would be executed if it was present on the source-code for the program (programmed as part of the software), using a GUI element, like jTextArea.
The following StackOverflow questions seem to be related, but, along with they'r answers, don't seem to be what i'm looking for.
How To Get Input From Console Class In Java?
Using GUI for console input and outputin java
I don't want to "be able to trigger actions from specific console inputs, and print the feedback into the console", as seems to be the case of console applications described in those question and answers.
What i want is to "be able to execute actual java code, that i cannot predict nor control, from console (or GUI) input".
NOTE: The "i cannot predict nor control" here refers to the "developer"...But of course i can predict and "control" it if i'm the one inputting the code, as the "user" would do.
Since java uses a virtual-machine environment, i think it might be possible for it to execute "run-time inputted code"...But i'm not sure such thing is even possible.
For example, i'd like the run-time input of for(int i=0; i<3; i++){System.out.println(i);} in the "GUI console" (jTextArea, for example) to, upon pressing the enter key or clicking a "Send" button, be ("compiled and "?) executed, and give the same output as if it was part of the original source-code, thus:
0
1
2
So i'd like to know the following:
Is it possible?
If yes, how can i do it? (OR, if no, what is the closest alternative?)

Use the JavaCompiler. It can compile code from a String.
For an E.G. see the STBC & especially the source code. It provides a GUI and can compile the code in the text area on button click.
But note the:
System Requirements
STBC will run on any computer with a version 1.6+ Java Plug-In* JDK (AKA SDK).
(*) The API that STBC uses is merely a public interface to the compiler in the tools.jar that is distributed only with JDKs (though the 'public JRE' of the JDK also seems to acquire a tools.jar). This leads to some unusual requirements in running either the native jar, or the web start app.

You can use JavaCompiler, as this question's answer states:
https://stackoverflow.com/a/935316/420001
Also, what you're wanting to do is evaluate a String of code:
It's not really recommended though.

There is a project called BeanShell
"In short, BeanShell is dynamically interpreted Java, plus a scripting language and flexible environment all rolled into one clean package. "

I know this is an old answer but for future Googlers:
I would recommend JavaREPL whose source is available here:
https://github.com/albertlatacz/java-repl
What AlmightyR is asking for is called Read-Eval-Print-Loop (REPL) for the Java language which is what JavaREPL provides.
JavaREPL has an online demo available here: http://www.javarepl.com/console.html
JavaREPL also has an Intellij plugin and a CLI version which are both linked to in the Github repository.
It looks sort of abandoned currently but perhaps it just doesn't need to be maintained?

How to put java code into an application format?

I made a simple command-line based game in java, only two classes (using Eclipse). But I was wondering how I can make this into a usable application for anyone, without running it through eclipse (ie send it to someone who knows nothing about java but would still be able to play the game)? Thanks!

You want to create a runnable jar file.
Eclipse has an option for this in the "Export" menu. For more options, search for "executable jar file" here or on Google.
You want to make sure that you also include any jar files your code depends on as well (Eclipse can also do that for you).
Users will be able to start this by double-clicking on the file on most platforms. If you need better integration (such as a custom icon), you will need to bundle it up further into an OS-specific executable. But for starters, a simple runnable jar works fine.
send it to someone who knows nothing about java
You need to get them to at least install the Java runtime on their machine (if it is not already there).

Just to be clear, "command-line" and "knows nothing about java" are probably not going to work very well for you given that:
java is OS agnostic, therefore, if you send (presumably) a jar file to say...your grandma and she has a mac and you have a PC chances are her getting it to work is not going to be "out of the box easy" so to speak.
Left with this, I think you have a couple choices...first off, you do need to package your classes - a runnable jar will work fine. Aside from that, you will most likely have to build OS specific scripts (batch scripts for Windows, shell scripts for unix, etc.) and you will have to hand these out with your jar file. That being said, the intended user will still need to have java installed, and the batch scripts themselves are not likely to be trivial endeavors.
Your next option would be to use JNLP. However, I don't think JNLP has a command line mode, so you will likely have to simulate a console with something like a JTextArea.
As far as I see it, your last option it to use one of the many products (not sure if there are any free ones) that package java into native code. I think Exe4j is one such example - but, like I said, I am not sure if there are any free ones and I am not sure how hard they are to use.
Best of luck, and if you can't get your jar to work you should probably move that to its own question.