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.
It means that constructor cannot be used by a class outside that particular package (unless the calling class extends the class with the protected constructor).
Why you might use a protected constructor is harder to explain. One possible implementation could be in some sort of creation pattern where all the classes that participate in the pattern sit in one package and you don't want classes outside this calling the constructor directly. [ September 02, 2008: Message edited by: Paul Sturrock ]