Googling for no main class netbeans shows that you aren't the only one to ever come across this problem.
Suggestions I found:
Make sure your project has a main class:
Right click on your Project in the project explorer
Click on properties
Click on Run
Make sure your Main Class is the one you want to be the entry point. (Make sure to use the fully qualified name i.e. mypackage.MyClass)
Otherwise, yeah try and "redo" ?
You might do well to stop using NetBeans; look here for an alternative suggestion, but ignore the telling off given another user.
You might do well also to create a Shape interface and make your abstract class implement that interface. Beware: all its subclasses will implicitly implement the same interface and all non‑abstract (properly called concrete) subclasses must therefore implement every method in that interface. Possible structure of such an interface:-You will realise that the 90% of that interface which consists of documentation comments (as I told you yesterday) is missing because I only took 30 seconds to write that code. Note that all methods are public and abstract implicitly even though you usually omit those two keywords.
I am currently taking online courses to get my Bachelor's degree in IT. One of my classes is Java Programming and we have to use Netbeans as our IDE. The program I put up is from a link our instructor gave us. We had to put it in Netbeans and add more to it, but when I put the information from the link I was getting those error messages. Programming is like a foreign language to me, I am trying so hard to understand. I have been spending hours online trying to figure out what I am supposed to do. When I think I just might have an idea of what is going on, I realize I am wrong. It is so disheartening. But, I need to get through this week and next, 7 more programs and hopefully keep my grade. Thank you and the others for all the help you give. Sorry for the novel, I just thought I should explain myself.
Debbie Thornton wrote:I am currently taking online courses to get my Bachelor's degree in IT. ... Programming is like a foreign language to me, I am trying so hard to understand. I have been spending hours online trying to figure out what I am supposed to do.
I would suggest, then, to hold your instructor, whom you hired to teach you, to teach you.
Fast forward: let's say you pass this course and check all the other boxes required for your BSIT. What next?
Freelance? You won't be equipped.
Get a job? You'll never pass the initial interview, assuming you got one, or the Oracle certification test that may be required to even get an interview.
Again, I suggest getting what you paid for.