# File lib/childprocess/jruby/process.rb, line 38
      def pid
        if @process.getClass.getName != "java.lang.UNIXProcess"
          raise NotImplementedError.new("pid is not supported by JRuby child processes on Windows")
        end

        # About the best way we can do this is with a nasty reflection-based impl
        # Thanks to Martijn Courteaux
        # http://stackoverflow.com/questions/2950338/how-can-i-kill-a-linux-process-in-java-with-sigkill-process-destroy-does-sigter/2951193#2951193
        field = @process.getClass.getDeclaredField("pid")
        field.accessible = true
        field.get(@process)
      end