I don't see you calling addActionListener () on it like you do the radio buttons, and you don't have anything in your actionPerformed () to handle when the source of the ActionEvent is the button.

Copy Listings 1 through 3 to Library.java, Book.java, and Author.java files that are stored in the same directory. Next, assuming that this directory is current, compile this source code as follows: ...

The Java platform’s tool support for creating external DSLs is pretty strong, however. You’ve walked through the steps of building an external DSL using openArchitectureWare and Xtext.