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.
"Unresolved compilation problem" indicates that you have multiple source files and that they are not in sync: you have class files somewhere from a previous version of the source code. The solution is to delete these old class files and recompile all the source code.