Save Data from Arduino to .txt with Processing

I didnt knew that it’s possible to save them in a table. That should be the better way.
Im not sure in some points:
1.) Does the storage into the table have to be in the “serialEvent” to make sure that I only save data if there are new data? If yes, what comes in draw? It seems like that it is not possible to let it open.
2.) How can I split the array, which I get from the Arduino (3 values) into several variables so i can storage them into my table?
I appreciate your support a lot!

Edit: Since my draw is empty I always get:

Error, disabling serialEvent() for COM4
Null

And I have no idea why. I also got it when I did it with the sketch before and a empty draw.