I don’t know why your wktFeature seems to be of type Feature, where it actually should be of type SimpleFeature.
You can try the following:
# create the SimpleFeature type at the beginning of your script once
SimpleFeature = jpy.get_type('org.opengis.feature.simple.SimpleFeature)
# later cast your wktFeature and set the value
simpleFeature = jpy.cast(wktFeature , SimpleFeature)
simpleFeature.setDefaultGeometry(geometry)
A similar issue happend here: