public Switch newSwitch(int id, int capacity) {
        Switch s = swBuilder.newSwitch(id, capacity);
        switches.add(s);
        return s;
    }
public Switch newSwitch ( int id , int capacity ) { Switch s = swBuilder . newSwitch ( id , capacity ) ; switches . add ( s ) ; return s ; }
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