Need not be called directly especially when using WorldBuilder

def step_options(args = {})
  default_step.merge(args)
   # now call the java method
  set_step(args[:time_step], args[:velocity_iter], args[:position_iter])
end

The default options

def default_step
  { time_step: 1.0 / 60, velocity_iter: 8, position_iter: 10 }
end