This week's book giveaway is in the OCAJP 8 forum. We're giving away four copies of OCA Java SE 8 Programmer I Study Guide and have Edward Finegan & Robert Liguori on-line! See this thread for details.
it means that main author used enum as a variable name and in java 5 enum is a keyword, so it return a compiler error as it is in violation ith language rules (the book is not for tomcat 5.5 and java 5)
you can use tomcat 5.5.x with an older jdk to compile the code with no error. but you will need tomcat compatibility pack to use tomcat 5.5 with jdk 1.4.x