Change
Camera cam = Camera.open();
Parameters p = cam.getParameters();
p.setFlashMode(Parameters.FLASH_MODE_OFF);
cam.setParameters(p);
cam.stopPreview();
cam.release();
return "Turning off";
to
cam.stopPreview();
cam.release();
return "Turning off";
I ran into a lot of these issues building an open source flashlight for Android which may help you with further questions.