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.
Which is just about never. All of the primitive-wrapper classes have static valueOf methods which may use cached objects, reducing the memory footprint of your application. You should use those as much as possible. I never use new in combination with the primitive-wrapper classes anymore.