code: public Switch newSwitch(int id, int capacity) {
          Switch s = swBuilder.newSwitch(id, capacity);
          switches.add(s);
          return s;
      }
docs: Create a new switch with a specific identifier and a given maximal capacity
  
  @param id       the switch identifier
  @param capacity the switch maximal capacity (put a nul or negative number for non-blocking switch)
  @return the switch