Before we start writing libraries, we need to install the Processing library template in Eclipse. This template will help us to package our library so we can easily distribute it to our audience.
Making libraries used to be a little painful, as setting up the project in Eclipse takes some knowledge of the environment and the build process. The Processing team has made a lot of effort in creating a template for Eclipse to streamline this process. You can download the template at http://code.google.com/p/processing/downloads, but you don't need to unzip the file.
Now that you've downloaded the Library template, it's time to install it in Eclipse so you can create your own library. If you are still in the Processing perspective, you'll need to switch back to the Java perspective. Go to the Window | Open Perspective | Other… menu, select the Java (default) perspective, and click the OK button.
Create a new Java Project...