code: public void selectFields(String[] fieldNames) {
  		checkNotNull(fieldNames, "fieldNames");
  		this.fieldNames = fieldNames;
  		RowTypeInfo rowTypeInfo = (RowTypeInfo) ParquetSchemaConverter.fromParquetType(expectedFileSchema);
  		TypeInformation[] selectFieldTypes = new TypeInformation[fieldNames.length];
  		for (int i = 0; i < fieldNames.length; i++) {
  			try {
  				selectFieldTypes[i] = rowTypeInfo.getTypeAt(fieldNames[i]);
  			} catch (IndexOutOfBoundsException e) {
  				throw new IllegalArgumentException(String.format("Fail to access Field %s , "
  						+ "which is not contained in the file schema", fieldNames[i]), e);
  			}
  		}
  		this.fieldTypes = selectFieldTypes;
  	}
docs: Configures the fields to be read and returned by the ParquetInputFormat. Selected fields must be present
  in the configured schema.
  
  @param fieldNames Names of all selected fields.