code: void addPropertyIfAbsent(final String name, final Object value) {
          final String currentValue = SecurityActions.getPropertyPrivileged(name);
          if (currentValue == null) {
              SecurityActions.setPropertyPrivileged(name, value.toString());
              propertiesToClear.add(name);
          }
      }
docs: Adds a system property only if the property does not currently exist. If the property does not exist on
  {@link #restore()} the property will be cleared.
  
  @param name  the name of the property
  @param value the value to set if the property is absent