code: private String getLongPrefix(String token) {
          String name = null;
          for (int i = token.length() - 2; i > 1; i--) {
              String prefix = token.substring(0, i);
              if (options.hasLongOption(prefix)) {
                  name = prefix;
                  break;
              }
          }
          return name;
      }
docs: Search for a prefix that is the long name of an option (-Xmx512m).
  
  @param token the command line token to handle