Yes, you can use an ArrayList to store the values as they come, because it is extensible. If you know in advance that the number of values is limited, just use a good old Array, it is more efficient.
To replay in reverse, you use an inverted for loop, starting at array's length-1, ending at 0, with decrement instead of increment.

Ok sounds good. Is there a limit to how big an ArrayList can be.  The application I am using it for has a potential to be thousands of values long.  My project is a robot that drives around based on joystick controls, then when you press a button, the robot does the entire path in reverse.  This is where the ArrayList comes in.  It would send out the motor values in reverse to drive in reverse.  Also, is the ArrayList laggy or slow? because missing one value could be the difference between a left turn and right turn in this project. 

I was thinking maybe I could use 2 arrays.  One to count the value and one to count how many times a value happens.

For example if the joystick was outputting:
0
0
0
0
1
2
3
3
5
5.

Then some how make an array that holds 0,1,2,3,4,5.  And also make an array that holds 4,1,1,2,2(the number of times each value appears).  However I am not sure how to do this or if this could even work.

Thanks a lot for the help,

-Ben

ArrayList should be fast enough, and can store as many data as you want, as long as you have enough memory (default settings should be OK for millions of numbers).
No need for two arrays, just make a simple class to store the pair of values (using it as a structure, not even need of a method in it). With a nice side effect of being more efficient (memory-wise and even speed-wise) than two separate lists.