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.
There is only a format string in the call: "12%1$s". This simply constructs a string with the contents "12" plus the first argument in the argument list using string conversion (basically, creates a string which is "12" concatenated with the second argument of the printf() call.)
All code in my posts, unless a source is explicitly mentioned, is my own.