This week's book giveaway is in the OCAJP 8 forum. We're giving away four copies of OCA Java SE 8 Programmer I Study Guide and have Edward Finegan & Robert Liguori on-line! See this thread for details.
The code as you have it above works fine for me. The only references I can find in a search involve JDBC. Are you giving us the full story here? Can you give us a short sample of code that exhibits this behavior?
Working with numbers and currencies is sometimes tricky. As suggested above, you may want to start using java.text.NumberFormat and its subclasses. They help in formatting different numbers and currencies.