automatic reload sketches in processing

I'd like to be more efficient with processing programming, is there a way to run a sketch from the command line? maybe also with a watch for file saves?

Also, is there some autocompletion for processing? the default IDE is very limited..

As @erisoco mentions, using the Eclipse IDE is your best bet (especially for autocomplete/etc.) and the Proclipsing plugin makes it very easy to setup Processing projects in eclipse (including integration with external libraries)

There's also a quick video tutorial on setup if necessary.

You mentioned "watch for file saves" - that sounds along the lines of "live coding". There are multiple options. One I've used in the past is through the FluidForms library. The library also includes some handy features for (3D) design (like parameter changer, automatic arcball for 3D scenes, STL export, etc.) You can find a few quick video tutorials on live coding Processing with Fluid Forms libs:

1. Fluid-Forms-Libs ~ HelloWorld
2. Fluid Forms Libs Parameter Changer
3. FluidFormsLibs-LiveCoding