setSpeed(float) on a EV3LargeRegulatedMotor is not implemented
The LeJos API offers a float-based setSpeed() method on BaseRegulatedMotor, which is a superclass of EV3LargeRegulatedMotor. So this implementation is not complete. This is only available as setSpeed(integer)
see: http://www.lejos.org/ev3/docs/lejos/hardware/motor/BaseRegulatedMotor.html and http://www.lejos.org/ev3/docs/lejos/hardware/motor/EV3LargeRegulatedMotor.html