The Sound problem from the 2011 AP Computer Science Exam is typical of free response problems that test arrays. The problem requires you to find and modify elements that exceed a given limit.
The AttractiveCritter problem from the 2011 AP Computer Science Exam is typical of free response problems that test GridWorld: The AP Computer Science Case Study. The problem requires you to extend the Critter class, determine which methods to override, and implement the entire subclass.
The RouteCipher problem from the 2011 AP Computer Science Exam is typical of free response problems that test 2 dimensional arrays. The problem requires you to traverse the array in row major order, which is most easily accomplished with a nested for loop.