@@ -6,7 +6,10 @@
 
 :author: Barthelemy Dagenais
 """
+from __future__ import annotations
+
 from threading import RLock
+from typing import Any
 
 
 class ThreadSafeFinalizer(object):
@@ -28,7 +31,7 @@ class ThreadSafeFinalizer(object):
     lock = RLock()
 
     @classmethod
-    def add_finalizer(cls, id, weak_ref):
+    def add_finalizer(cls, id: Any, weak_ref: Any) -> None:
         """Registers a finalizer with an id.
 
         :param id: The id of the object referenced by the weak reference.
@@ -38,7 +41,7 @@ def add_finalizer(cls, id, weak_ref):
             cls.finalizers[id] = weak_ref
 
     @classmethod
-    def remove_finalizer(cls, id):
+    def remove_finalizer(cls, id: Any) -> None:
         """Removes a finalizer associated with this id.
 
         :param id: The id of the object for which the finalizer will be
@@ -48,7 +51,7 @@ def remove_finalizer(cls, id):
             cls.finalizers.pop(id, None)
 
     @classmethod
-    def clear_finalizers(cls, clear_all=False):
+    def clear_finalizers(cls, clear_all: bool = False) -> None:
         """Removes all registered finalizers.
 
         :param clear_all: If `True`, all finalizers are deleted. Otherwise,
 
@@ -9,19 +9,23 @@
 
 :author: Barthelemy Dagenais
 """
+from __future__ import annotations
+
 from collections import deque
 import logging
 import os
 from pydoc import pager
 from queue import Queue
 import select
 import socket
+import ssl
 import struct
 from subprocess import Popen, PIPE
 import subprocess
 import sys
 import traceback
 from threading import Thread, RLock
+from typing import Any
 import weakref
 
 from py4j.compat import hasattr2
@@ -190,7 +194,7 @@ def deprecated(name, last_version, use_instead="", level=logging.DEBUG,
         raise DeprecationWarning(msg)
 
 
-def java_import(jvm_view, import_str):
+def java_import(jvm_view: Any, import_str: str) -> None:
     """Imports the package or class specified by `import_str` in the
     jvm view namespace.
 
@@ -242,12 +246,21 @@ def find_jar_path():
     return ""
 
 
-def launch_gateway(port=0, jarpath="", classpath="", javaopts=[],
-                   die_on_exit=False, redirect_stdout=None,
-                   redirect_stderr=None, daemonize_redirect=True,
-                   java_path="java", create_new_process_group=False,
-                   enable_auth=False, cwd=None, return_proc=False,
-                   use_shell=False):
+def launch_gateway(
+        port: int = 0,
+        jarpath: str = "",
+        classpath: str = "",
+        javaopts: list[str] = [],
+        die_on_exit: bool = False,
+        redirect_stdout: Any = None,
+        redirect_stderr: Any = None,
+        daemonize_redirect: bool = True,
+        java_path: str = "java",
+        create_new_process_group: bool = False,
+        enable_auth: bool = False,
+        cwd: str | None = None,
+        return_proc: bool = False,
+        use_shell: bool = False) -> int | tuple[int, Popen] | tuple[int, str] | tuple[int, str, Popen]:
     """Launch a `Gateway` in a new Java process.
 
     The redirect parameters accept file-like objects, Queue, or deque. When
@@ -397,7 +410,7 @@ def launch_gateway(port=0, jarpath="", classpath="", javaopts=[],
     return output
 
 
-def get_field(java_object, field_name):
+def get_field(java_object: Any, field_name: str) -> Any:
     """Retrieves the field named `field_name` from the `java_object`.
 
     This function is useful when `auto_field=false` in a gateway or
@@ -422,7 +435,7 @@ def get_field(java_object, field_name):
             field_name)
 
 
-def set_field(java_object, field_name, value):
+def set_field(java_object: Any, field_name: str, value: Any) -> None:
     """Sets the field named `field_name` of `java_object` to `value`.
 
     This function is the only way to set a field because the assignment
@@ -468,7 +481,7 @@ def get_method(java_object, method_name):
         java_object._gateway_client)
 
 
-def is_instance_of(gateway, java_object, java_class):
+def is_instance_of(gateway: JavaGateway, java_object: Any, java_class: Any) -> bool:
     """Indicates whether a java object is an instance of the provided
     java_class.
 
@@ -779,10 +792,17 @@ class GatewayParameters(object):
     """
 
     def __init__(
-            self, address=DEFAULT_ADDRESS, port=DEFAULT_PORT, auto_field=False,
-            auto_close=True, auto_convert=False, eager_load=False,
-            ssl_context=None, enable_memory_management=True,
-            read_timeout=None, auth_token=None):
+            self,
+            address: str = DEFAULT_ADDRESS,
+            port: int = DEFAULT_PORT,
+            auto_field: bool = False,
+            auto_close: bool = True,
+            auto_convert: bool = False,
+            eager_load: bool = False,
+            ssl_context: ssl.SSLContext | None = None,
+            enable_memory_management: bool = True,
+            read_timeout: float | None = None,
+            auth_token: str | None = None) -> None:
         """
         :param address: the address to which the client will request a
             connection. If you're assing a `SSLContext` with
@@ -842,12 +862,17 @@ class CallbackServerParameters(object):
     """
 
     def __init__(
-            self, address=DEFAULT_ADDRESS, port=DEFAULT_PYTHON_PROXY_PORT,
-            daemonize=False, daemonize_connections=False, eager_load=True,
-            ssl_context=None,
-            accept_timeout=DEFAULT_ACCEPT_TIMEOUT_PLACEHOLDER,
-            read_timeout=None, propagate_java_exceptions=False,
-            auth_token=None):
+            self,
+            address: str = DEFAULT_ADDRESS,
+            port: int = DEFAULT_PYTHON_PROXY_PORT,
+            daemonize: bool = False,
+            daemonize_connections: bool = False,
+            eager_load: bool = True,
+            ssl_context: ssl.SSLContext | None = None,
+            accept_timeout: float | str = DEFAULT_ACCEPT_TIMEOUT_PLACEHOLDER,
+            read_timeout: float | None = None,
+            propagate_java_exceptions: bool = False,
+            auth_token: str | None = None) -> None:
         """
         :param address: the address to which the client will request a
             connection
@@ -1843,12 +1868,17 @@ class JavaGateway(object):
     """
 
     def __init__(
-            self, gateway_client=None, auto_field=False,
-            python_proxy_port=DEFAULT_PYTHON_PROXY_PORT,
-            start_callback_server=False, auto_convert=False, eager_load=False,
-            gateway_parameters=None, callback_server_parameters=None,
-            python_server_entry_point=None,
-            java_process=None):
+            self,
+            gateway_client: GatewayClient | None = None,
+            auto_field: bool = False,
+            python_proxy_port: int = DEFAULT_PYTHON_PROXY_PORT,
+            start_callback_server: bool = False,
+            auto_convert: bool = False,
+            eager_load: bool = False,
+            gateway_parameters: GatewayParameters | None = None,
+            callback_server_parameters: CallbackServerParameters | None = None,
+            python_server_entry_point: Any = None,
+            java_process: Popen | None = None) -> None:
         """
         :param gateway_parameters: An instance of `GatewayParameters` used to
             configure the various options of the gateway.
 
@@ -16,9 +16,15 @@
 
 :author: Barthelemy Dagenais
 """
+from __future__ import annotations
+
 from base64 import standard_b64encode, standard_b64decode
 
 from decimal import Decimal
+from typing import Any, TYPE_CHECKING
+
+if TYPE_CHECKING:
+    from py4j.java_gateway import PythonProxyPool
 
 
 JAVA_MAX_INT = 2147483647
@@ -168,7 +174,7 @@
 EMPTY_RESPONSE = "empty_response"
 
 
-def escape_new_line(original):
+def escape_new_line(original: str | bytes) -> str:
     """Replaces new line characters by a backslash followed by a n.
 
     Backslashes are also escaped by another backslash.
@@ -197,7 +203,7 @@ def escape_new_line(original):
         return original
 
 
-def unescape_new_line(escaped):
+def unescape_new_line(escaped: str) -> str:
     """Replaces escaped characters by unescaped characters.
 
     For example, double backslashes are replaced by a single backslash.
@@ -218,7 +224,7 @@ def unescape_new_line(escaped):
         return escaped
 
 
-def smart_decode(s):
+def smart_decode(s: bytes | str) -> str:
     if isinstance(s, str):
         return s
     elif isinstance(s, bytes):
@@ -227,7 +233,7 @@ def smart_decode(s):
         return str(s)
 
 
-def encode_float(float_value):
+def encode_float(float_value: float) -> str:
     # str(float) on Python 3 already returns the same shortest-
     # roundtrip repr that smart_decode(repr(...)) was producing on
     # py2; smart_decode here was a no-op dispatcher.
@@ -241,15 +247,15 @@ def encode_float(float_value):
     return float_str
 
 
-def encode_bytearray(barray):
+def encode_bytearray(barray: bytes | bytearray) -> str:
     if isinstance(barray, bytes):
         return str(standard_b64encode(barray), encoding="ascii")
     else:
         newbytestr = bytes(barray)
         return str(standard_b64encode(newbytestr), encoding="ascii")
 
 
-def decode_bytearray(encoded):
+def decode_bytearray(encoded: str) -> bytes:
     # Per @PaperTsar's analysis in issue #570: the prior
     # implementation built a Python list of ints (one PyObject per
     # byte) then reconstructed bytes from that list — pure overhead
@@ -260,7 +266,7 @@ def decode_bytearray(encoded):
     return bytes(standard_b64decode(encoded.encode("ascii")))
 
 
-def is_python_proxy(parameter):
+def is_python_proxy(parameter: object) -> bool:
     """Determines whether parameter is a Python Proxy, i.e., it has a Java
     internal class with an `implements` member.
 
@@ -275,7 +281,7 @@ def is_python_proxy(parameter):
     return is_proxy
 
 
-def get_command_part(parameter, python_proxy_pool=None):
+def get_command_part(parameter: object, python_proxy_pool: PythonProxyPool | None = None) -> str:
     """Converts a Python object into a string representation respecting the
     Py4J protocol.
 
@@ -317,7 +323,7 @@ def get_command_part(parameter, python_proxy_pool=None):
     return command_part
 
 
-def get_return_value(answer, gateway_client, target_id=None, name=None):
+def get_return_value(answer: str, gateway_client: Any, target_id: str | None = None, name: str | None = None) -> Any:
     """Converts an answer received from the Java gateway into a Python object.
 
     For example, string representation of integers are converted to Python
@@ -399,14 +405,14 @@ def compute_exception_message(default_message, extra_message=None):
     return message
 
 
-def is_error(answer):
+def is_error(answer: str) -> tuple[bool, None]:
     if len(answer) == 0 or answer[0] != SUCCESS:
         return (True, None)
     else:
         return (False, None)
 
 
-def is_fatal_error(answer):
+def is_fatal_error(answer: str) -> bool:
     return answer and len(answer) > 0 and answer[0] == FATAL_ERROR
 
 
@@ -455,21 +461,21 @@ def register_input_converter(converter, prepend=False):
 class Py4JError(Exception):
     """Exception raised when a problem occurs with Py4J."""
 
-    def __init__(self, args=None, cause=None):
+    def __init__(self, args: str | None = None, cause: BaseException | None = None) -> None:
         super().__init__(args)
         self.cause = cause
 
 
 class Py4JAuthenticationError(Py4JError):
     """Exception raised when Py4J cannot authenticate a connection."""
-    def __init__(self, args=None, cause=None):
+    def __init__(self, args: str | None = None, cause: BaseException | None = None) -> None:
         super().__init__(args)
         self.cause = cause
 
 
 class Py4JNetworkError(Py4JError):
     """Exception raised when a network error occurs with Py4J."""
-    def __init__(self, args=None, cause=None, when=None):
+    def __init__(self, args: str | None = None, cause: BaseException | None = None, when: str | None = None) -> None:
         super().__init__(args)
         self.cause = cause
         self.when = when
@@ -486,7 +492,7 @@ class Py4JJavaError(Py4JError):
 
     """
 
-    def __init__(self, msg, java_exception):
+    def __init__(self, msg: str, java_exception: Any) -> None:
         self.args = (msg, java_exception)
         self.errmsg = msg
         self.java_exception = java_exception
 
@@ -3,8 +3,11 @@
 The signals pattern is very similar to the listener/observer pattern.
 
 """
+from __future__ import annotations
+
 from inspect import ismethod
 from threading import Lock
+from typing import Any, Callable
 
 
 def make_id(func):
@@ -33,7 +36,7 @@ def __init__(self):
         # number of receivers to be very small.
         self.receivers = []
 
-    def connect(self, receiver, sender=None, unique_id=None):
+    def connect(self, receiver: Callable[..., Any], sender: object = None, unique_id: Any = None) -> None:
         """Registers a receiver for this signal.
 
         The receiver must be a callable (e.g., function or instance method)
@@ -58,7 +61,7 @@ def connect(self, receiver, sender=None, unique_id=None):
             else:
                 self.receivers.append((full_id, receiver))
 
-    def disconnect(self, receiver, sender=None, unique_id=None):
+    def disconnect(self, receiver: Callable[..., Any], sender: object = None, unique_id: Any = None) -> bool:
         """Unregisters a receiver for this signal.
 
         :param receiver: The callable that was registered to receive the
@@ -82,7 +85,7 @@ def disconnect(self, receiver, sender=None, unique_id=None):
 
         return disconnected
 
-    def send(self, sender, **params):
+    def send(self, sender: object, **params: Any) -> list[tuple[Callable[..., Any], Any]]:
         """Sends the signal to all connected receivers.
 
         If a receiver raises an error, the error is propagated back and