Processing's "millis()" method returns the number of milliseconds since the start of the sketch. You can save it to a variable, run your code, and then call it again and compute the time elapsed for the code to run. For instance:

In Processing, i'm usually more interested in frame rates than code speed.  If your code is fast, frame rates are high.  You can observe the value of the frameRate variable to see the frame rate.

thanks guys :)