Actually that’s the tricky part to instantiate an inner class! 
B/c even before instantiating an inner class, an instance of its enclosing class needs to exist 1st. 
In our case, the enclosing class instance is the sketch itself, a subclass of PApplet. 
There’s a small bug in your posterity solution: 
B/c variable innerCls isn’t initialized right way, that’ll never happen if the try {} fails! 
You can replace System.err.println(ex); w/ throw new RuntimeException(ex); inside the catch () {} block in order to override that. 
Posterity Code amended…