parquet-cli/src/main/java/org/apache/parquet/cli/BaseCommand.java
public InputStream open(String filename) throws IOException {
    if (STDIN_AS_SOURCE.equals(filename)) {
      return System.in;
    }

    URI uri = qualifiedURI(filename);
    if (RESOURCE_URI_SCHEME.equals(uri.getScheme())) {
      return Resources.getResource(uri.getRawSchemeSpecificPart()).openStream();
    } else {
      Path filePath = new Path(uri);
      // even though it was qualified using the default FS, it may not be in it
      FileSystem fs = filePath.getFileSystem(getConf());
      return fs.open(filePath);
    }
  }
public InputStream open(String filename) throws IOException {
    if (STDIN_AS_SOURCE.equals(filename)) {
      return System.in;
    }

    URI uri = qualifiedURI(filename);
    if (RESOURCE_URI_SCHEME.equals(uri.getScheme())) {
      return Resources.getResource(uri.getRawSchemeSpecificPart()).openStream();
    } else {
      Path filePath = new Path(uri);
      // even though it was qualified using the default FS, it may not be in it
      FileSystem fs = filePath.getFileSystem(getConf());
      return fs.open(filePath);
    }
  }
Opens an existing file or resource.

If the file does not have a file system scheme, this uses the default FS.

@param filename The filename to open.
@return An open InputStream with the file contents
@throws IOException if there is an error opening the file
@throws IllegalArgumentException If the file does not exist