Here is or team's Java code for getting the Rev Robotics Digit board to display text. The code is in the team 1493 GitHub:
https://github.com/FIRSTteam1493/Rev...rd/tree/master
The character repository contains the byte binary codes for each character (note that each character takes up two elements in the array). Characters are printed from right to left on the 14-segment displays (so the first character in byte1 will end up in the rightmost display). You store whatever you want to print in byte1, then run i2c.writeBulk(byte1) to write it to the board's internal RAM and therefore to the displays. Right now the code is set to cycle through all 36 characters, but you can change that to whatever you want.
Cheers!
-1493