code: public static TableRef valueOf(String catalog, String schema, String tableName) {
          return new TableRef(catalog, schema, tableName);
      }
docs: Creates an instance from catalog, schema and table names
  <p/>
  <p>if the catalog or schema parameter is an empty String, the catalog or schema will be set to
  <code>null</code>.</p>
  
  @param catalog   the table catalog
  @param schema    the table schema
  @param tableName the table name
  @return a <code>TableRef</code> for the table identified by the specified catalog, schema and table name.
  @throws IllegalArgumentException if the tableName parameter is null