You have to delete a class in order to compile your library? Could you provide a more detailed explanation?

Yes, Eclipse is supposed to do the clean up itself, no need for manual deletion.
We lack background, like are you experienced in debugging in Eclipse in general (I suppose no).
You can find lot of tutorials on this task, starting with the help in Eclipse itself.

Thanks a lot for the help.

When I test a library, I compile it and then start Processing, import the library, and write a sketch that uses it. Libraries should behave quite differently within a Java environment and within a Processing environment.

So, there is no chance to check the library before you compile it?

That's what I do, at least... it normally won't take all that long to compile (twenty seconds for a large library), and the PDE is where users of your library will be developing. The only inconvenience with this approach is that you have to restart the PDE every time. You fall into a different kind of rhythm... with less emphasis on testing and more emphasis on coding.

The best way to test your library is to create a second Eclipse project purely for testing purposes.

Let us assume that your Eclipse library project is called ABC123 and that it is based on the library template and the project compiles and the ant build file runs OK.

Now you want to test it in Eclipse without having to change the library project. Create another Eclipse Java project and call it ABC123 Testing, this will keep the projects together in the Project view. once created right click on the test project name and select Build Path | Configure Build Path then click on the Projects tab and add your library project. This project can now access all the classes in your library project so there is no restriction on the number of test classes you can create.

This is what I do for my libraries.

HTH

Hello quarks, 

In Eclipse, there is no need to copy and paste classes in that way... and he described the process pretty well. Right-click (or control-click) on your test project, select Build Path >  Configure Build Path. From here, go to the Projects tab, click Add, and check your library project. Now, within your class files, you can import your library.

yes this Is what I did.

thanks Again Quarks!!!