How to use the py4j.java_gateway.get_java_class function in py4j

def _from_j_state_backend(j_state_backend):
    if j_state_backend is None:
        return None
    gateway = get_gateway()
    JStateBackend = gateway.jvm.org.apache.flink.runtime.state.StateBackend
    JMemoryStateBackend = gateway.jvm.org.apache.flink.runtime.state.memory.MemoryStateBackend
    JFsStateBackend = gateway.jvm.org.apache.flink.runtime.state.filesystem.FsStateBackend
    JRocksDBStateBackend = gateway.jvm.org.apache.flink.contrib.streaming.state.RocksDBStateBackend
    j_clz = j_state_backend.getClass()

    if not get_java_class(JStateBackend).isAssignableFrom(j_clz):
        raise TypeError("The input %s is not an instance of StateBackend." % j_state_backend)

    if get_java_class(JMemoryStateBackend).isAssignableFrom(j_state_backend.getClass()):
        return MemoryStateBackend(j_memory_state_backend=j_state_backend)
    elif get_java_class(JFsStateBackend).isAssignableFrom(j_state_backend.getClass()):
        return FsStateBackend(j_fs_state_backend=j_state_backend)
    elif get_java_class(JRocksDBStateBackend).isAssignableFrom(j_state_backend.getClass()):
        return RocksDBStateBackend(j_rocks_db_state_backend=j_state_backend)
    else:
        return CustomStateBackend(j_state_backend)  # users' customized state backend

def _is_instance_of(java_data_type, java_class):
    gateway = get_gateway()
    if isinstance(java_class, basestring):
        param = java_class
    elif isinstance(java_class, JavaClass):
        param = get_java_class(java_class)
    elif isinstance(java_class, JavaObject):
        if not _is_instance_of(java_class, gateway.jvm.Class):
            param = java_class.getClass()
        else:
            param = java_class
    else:
        raise TypeError(
            "java_class must be a string, a JavaClass, or a JavaObject")

    return gateway.jvm.org.apache.flink.api.python.shaded.py4j.reflection.TypeUtil.isInstanceOf(
        param, java_data_type)

def _is_instance_of(java_data_type, java_class):
    gateway = get_gateway()
    if isinstance(java_class, str):
        param = java_class
    elif isinstance(java_class, JavaClass):
        param = get_java_class(java_class)
    elif isinstance(java_class, JavaObject):
        if not _is_instance_of(java_class, gateway.jvm.Class):
            param = java_class.getClass()
        else:
            param = java_class
    else:
        raise TypeError(
            "java_class must be a string, a JavaClass, or a JavaObject")

    return gateway.jvm.org.apache.flink.api.python.shaded.py4j.reflection.TypeUtil.isInstanceOf(
        param, java_data_type)

def _from_j_restart_strategy(j_restart_strategy):
        if j_restart_strategy is None:
            return None
        gateway = get_gateway()
        NoRestartStrategyConfiguration = gateway.jvm.RestartStrategies\
            .NoRestartStrategyConfiguration
        FixedDelayRestartStrategyConfiguration = gateway.jvm.RestartStrategies\
            .FixedDelayRestartStrategyConfiguration
        FailureRateRestartStrategyConfiguration = gateway.jvm.RestartStrategies\
            .FailureRateRestartStrategyConfiguration
        FallbackRestartStrategyConfiguration = gateway.jvm.RestartStrategies\
            .FallbackRestartStrategyConfiguration
        clz = j_restart_strategy.getClass()
        if clz.getName() == get_java_class(NoRestartStrategyConfiguration).getName():
            return RestartStrategies.NoRestartStrategyConfiguration(
                j_restart_strategy=j_restart_strategy)
        elif clz.getName() == get_java_class(FixedDelayRestartStrategyConfiguration).getName():
            return RestartStrategies.FixedDelayRestartStrategyConfiguration(
                j_restart_strategy=j_restart_strategy)
        elif clz.getName() == get_java_class(FailureRateRestartStrategyConfiguration).getName():
            return RestartStrategies.FailureRateRestartStrategyConfiguration(
                j_restart_strategy=j_restart_strategy)
        elif clz.getName() == get_java_class(FallbackRestartStrategyConfiguration).getName():
            return RestartStrategies.FallbackRestartStrategyConfiguration(
                j_restart_strategy=j_restart_strategy)
        else:
            raise Exception("Unsupported java RestartStrategyConfiguration: %s" % clz.getName())

def _from_j_state_backend(j_state_backend):
    if j_state_backend is None:
        return None
    gateway = get_gateway()
    JStateBackend = gateway.jvm.org.apache.flink.runtime.state.StateBackend
    JMemoryStateBackend = gateway.jvm.org.apache.flink.runtime.state.memory.MemoryStateBackend
    JFsStateBackend = gateway.jvm.org.apache.flink.runtime.state.filesystem.FsStateBackend
    JRocksDBStateBackend = gateway.jvm.org.apache.flink.contrib.streaming.state.RocksDBStateBackend
    j_clz = j_state_backend.getClass()

    if not get_java_class(JStateBackend).isAssignableFrom(j_clz):
        raise TypeError("The input %s is not an instance of StateBackend." % j_state_backend)

    if get_java_class(JMemoryStateBackend).isAssignableFrom(j_state_backend.getClass()):
        return MemoryStateBackend(j_memory_state_backend=j_state_backend)
    elif get_java_class(JFsStateBackend).isAssignableFrom(j_state_backend.getClass()):
        return FsStateBackend(j_fs_state_backend=j_state_backend)
    elif get_java_class(JRocksDBStateBackend).isAssignableFrom(j_state_backend.getClass()):
        return RocksDBStateBackend(j_rocks_db_state_backend=j_state_backend)
    else:
        return CustomStateBackend(j_state_backend)  # users' customized state backend

def _from_j_state_backend(j_state_backend):
    if j_state_backend is None:
        return None
    gateway = get_gateway()
    JStateBackend = gateway.jvm.org.apache.flink.runtime.state.StateBackend
    JMemoryStateBackend = gateway.jvm.org.apache.flink.runtime.state.memory.MemoryStateBackend
    JFsStateBackend = gateway.jvm.org.apache.flink.runtime.state.filesystem.FsStateBackend
    JRocksDBStateBackend = gateway.jvm.org.apache.flink.contrib.streaming.state.RocksDBStateBackend
    j_clz = j_state_backend.getClass()

    if not get_java_class(JStateBackend).isAssignableFrom(j_clz):
        raise TypeError("The input %s is not an instance of StateBackend." % j_state_backend)

    if get_java_class(JMemoryStateBackend).isAssignableFrom(j_state_backend.getClass()):
        return MemoryStateBackend(j_memory_state_backend=j_state_backend)
    elif get_java_class(JFsStateBackend).isAssignableFrom(j_state_backend.getClass()):
        return FsStateBackend(j_fs_state_backend=j_state_backend)
    elif get_java_class(JRocksDBStateBackend).isAssignableFrom(j_state_backend.getClass()):
        return RocksDBStateBackend(j_rocks_db_state_backend=j_state_backend)
    else:
        return CustomStateBackend(j_state_backend)  # users' customized state backend

Because the options are not serializable and hold native code references,
        they must be specified through a factory.

        The options created by the factory here are applied on top of the pre-defined
        options profile selected via :func:`set_predefined_options`.
        If the pre-defined options profile is the default (:data:`PredefinedOptions.DEFAULT`),
        then the factory fully controls the RocksDB options.

        :param options_factory_class_name: The fully-qualified class name of the options
                                           factory in Java that lazily creates the RocksDB options.
                                           The options factory must have a default constructor.
        """
        gateway = get_gateway()
        JOptionsFactory = gateway.jvm.org.apache.flink.contrib.streaming.state.OptionsFactory
        j_options_factory_clz = load_java_class(options_factory_class_name)
        if not get_java_class(JOptionsFactory).isAssignableFrom(j_options_factory_clz):
            raise ValueError("The input class not implements OptionsFactory.")
        self._j_rocks_db_state_backend.setOptions(j_options_factory_clz.newInstance())

if table_config is not None:
            j_tenv = gateway.jvm.StreamTableEnvironment.create(
                stream_execution_environment._j_stream_execution_environment,
                table_config._j_table_config)
        elif environment_settings is not None:
            if not environment_settings.is_streaming_mode():
                raise ValueError("The environment settings for StreamTableEnvironment must be "
                                 "set to streaming mode.")
            j_tenv = gateway.jvm.StreamTableEnvironment.create(
                stream_execution_environment._j_stream_execution_environment,
                environment_settings._j_environment_settings)
        else:
            j_tenv = gateway.jvm.StreamTableEnvironment.create(
                stream_execution_environment._j_stream_execution_environment)
        j_planner_class = j_tenv.getPlanner().getClass()
        j_blink_planner_class = get_java_class(
            get_gateway().jvm.org.apache.flink.table.planner.delegation.PlannerBase)
        is_blink_planner = j_blink_planner_class.isAssignableFrom(j_planner_class)
        return StreamTableEnvironment(j_tenv, is_blink_planner)

return None
    gateway = get_gateway()
    JStateBackend = gateway.jvm.org.apache.flink.runtime.state.StateBackend
    JMemoryStateBackend = gateway.jvm.org.apache.flink.runtime.state.memory.MemoryStateBackend
    JFsStateBackend = gateway.jvm.org.apache.flink.runtime.state.filesystem.FsStateBackend
    JRocksDBStateBackend = gateway.jvm.org.apache.flink.contrib.streaming.state.RocksDBStateBackend
    j_clz = j_state_backend.getClass()

    if not get_java_class(JStateBackend).isAssignableFrom(j_clz):
        raise TypeError("The input %s is not an instance of StateBackend." % j_state_backend)

    if get_java_class(JMemoryStateBackend).isAssignableFrom(j_state_backend.getClass()):
        return MemoryStateBackend(j_memory_state_backend=j_state_backend)
    elif get_java_class(JFsStateBackend).isAssignableFrom(j_state_backend.getClass()):
        return FsStateBackend(j_fs_state_backend=j_state_backend)
    elif get_java_class(JRocksDBStateBackend).isAssignableFrom(j_state_backend.getClass()):
        return RocksDBStateBackend(j_rocks_db_state_backend=j_state_backend)
    else:
        return CustomStateBackend(j_state_backend)  # users' customized state backend