docs: public static synchronized final void init ( Properties props ) throws CIFSException {
          if ( INSTANCE != null ) {
              throw new CIFSException("Singleton context is already initialized");
          }
          Properties p = new Properties();
          try {
              String filename = System.getProperty("jcifs.properties");
              if ( filename != null && filename.length() > 1 ) {
  
                  try ( FileInputStream in = new FileInputStream(filename) ) {
                      p.load(in);
                  }
              }
  
          }
          catch ( IOException ioe ) {
              log.error("Failed to load config", ioe); //$NON-NLS-1$
          }
          p.putAll(System.getProperties());
          if ( props != null ) {
              p.putAll(props);
          }
          INSTANCE = new SingletonContext(p);
      }