There are couple of ways to get your application out of JBuilder. These depend on type of your applicaiton.

I guess that it is an ordenary application with GUI and not a webApp.

1. Go to wizards|archive builder
   
2. Choose application from the archivet type drop down list.
   
3. The steps are selfexplanetory, however, here are a few pointers.
   
4. In step 3, if you don't want all the classes in your project to be included in the JAR file you have to choose which ones you want.
   
5. In step 4, if you use any other libraries then the standard Java libraries, you can add them to your JAR file, otherwise you'll have to put them in your classpath.
   
6. In step 6, you have to choose your driver class. I.e. the class that starts your application, often a class with main in it.
   

Now you get a new icon in the project tree, right click on it and choos make.

Now you should have a JAR file that is runnable from the command line.

Should be something like, java -jar yourapp.jar.

Good Luck!