Just a quick question. Are you reading the errors or just posting them here? It's ok if you are because they aren't the most lovely things to read (though you should try. It'll be much faster) What it's giving you is what's called a stack trace. It basically tells you the path the code took before it got an error. I've added a comment on what the error tells you.
Code:
ERROR Unhandled exception: java.lang.IllegalArgumentException: Subsystem must not be null. at [
edu.wpi.first.wpilibj.command.Command.requires(Com mand.java:194), #6
org.usfirst.frc.team4623.robot.commands.Extend.<in it>(Extend.java:16), #5
^------------This is the file-------------------------^---------------Line #- ^
org.usfirst.frc.team4623.robot.OI.<init>(OI.java:5 6), #4
org.usfirst.frc.team4623.robot.Robot.robotInit(Rob ot.java:44), #3
du.wpi.first.wpilibj.IterativeRobot.startCompetit ion(IterativeRobot.java:72), #2
edu.wpi.first.wpilibj.RobotBase.main(RobotBase.jav a:241)] #1
So you start at the bottom and read up. Notice how it goes to robotInit at #3, then goes into OI at 4, then to the Extend class. At Line 16 (note my comment in the code) is where the error is. Looking at line 16 in the code shows
Code:
requires(Robot.pnue);
Looking in the Robot class I can see pneu, but the problem is it's initialized AFTER OI. So OI is looking for a null object, hence the error. Try putting OI after everything.