This week's book giveaway is in the OO, Patterns, UML and Refactoring forum. We're giving away four copies of Refactoring for Software Design Smells: Managing Technical Debt and have Girish Suryanarayana, Ganesh Samarthyam & Tushar Sharma on-line! See this thread for details.
This is thrown from Integer.parseInt(String) when the value you try to parse cannot be interpreted as an integer. Look at the code on line 18 of your CollectionDetails servlet and check the value you are trying to parse is not null and a parsable value (i.e. its not a letter or a floating point number, or some other non-numeric character)