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.
A number is just a number. It doesn't have a format by itself. There's no difference between a double that holds the value '9999' and one thatholds the value '9999.0'. When you convert the number to a string, in order to display it, then you specify how it should be formatted, for example with a certain number of decimal digits.