I have recently updated all the code for Head First Design Patterns to be compatible with Java 8. This new code will accompany an update for the book, to be released later in 2014.
Download the code and compile and run from the command line, or load the code into project in Eclipse (Kepler, with the Java 8 beta patch).
https://wiki.eclipse.org/JDT/Eclipse_Java_8_Support_For_Kepler