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.
Look at the API docs for the Math class. There is no method that takes (float, long) as arguments to it looks for the best match signature. Since a long can be automatically cast to float it calls the (float, float) version. Note that there may be precision loss in the conversion from long to float.