code: @SuppressWarnings("unchecked")
     public <UNIT extends TimeUnit> UNIT getUnit(final Class<UNIT> unitType)
     {
        if (unitType == null)
           return null;
  
        for (TimeUnit unit : units.keySet()) {
           if (unitType.isAssignableFrom(unit.getClass()))
           {
              return (UNIT) unit;
           }
        }
        return null;
     }
docs: Get the registered {@link TimeUnit} for the given {@link TimeUnit} type or <code>null</code> if none exists.