code: public Table updateTableDescription(String datasetName, String tableName, String newDescription) {
      // [START bigquery_update_table_description]
      // String datasetName = "my_dataset_name";
      // String tableName = "my_table_name";
      // String newDescription = "new_description";
  
      Table beforeTable = bigquery.getTable(datasetName, tableName);
      TableInfo tableInfo = beforeTable.toBuilder().setDescription(newDescription).build();
      Table afterTable = bigquery.update(tableInfo);
      // [END bigquery_update_table_description]
      return afterTable;
    }
docs: Example of updating a table by changing its description.