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.
byte, short, int, and long are all "integral types", meaning they can only represent integers -- numbers with no fractional parts. None of those types can hold 3.14, but they can hold 3. float and double are "floating point types", and they can represent numbers with fractional parts.