From f1486ada643cb586a6f62a02e8cd68088c63a710 Mon Sep 17 00:00:00 2001
From: Andrew Strelsky <46897303+astrelsky@users.noreply.github.com>
Date: Sun, 1 Sep 2024 13:32:41 -0400
Subject: [PATCH] "Generic" JArray support

---
 jpype/_core.py               |  1 +
 jpype/_jarray.py             | 38 +++++++++++++++++++++++++++++++++++-
 jpype/_jclass.py             |  5 +++++
 native/python/pyjp_class.cpp |  5 +++--
 test/jpypetest/test_array.py | 12 ++++++++++++
 5 files changed, 58 insertions(+), 3 deletions(-)

diff --git a/jpype/_core.py b/jpype/_core.py
index ca1191d01..1bb940289 100644
--- a/jpype/_core.py
+++ b/jpype/_core.py
@@ -339,6 +339,7 @@ def initializeResources():
     _jpype._type_classes[object] = _jpype._java_lang_Object
     _jpype._type_classes[_jpype.JString] = _jpype._java_lang_String
     _jpype._type_classes[_jpype.JObject] = _jpype._java_lang_Object
+    _jpype._type_classes[_jpype.JClass] = _jpype._java_lang_Class
     _jinit.runJVMInitializers()
 
     _jpype.JClass('org.jpype.JPypeKeywords').setKeywords(
diff --git a/jpype/_jarray.py b/jpype/_jarray.py
index 34ce2bd86..25309fcdb 100644
--- a/jpype/_jarray.py
+++ b/jpype/_jarray.py
@@ -15,14 +15,34 @@
 #   See NOTICE file for details.
 #
 # *****************************************************************************
+import abc
+import collections.abc
 import _jpype
+import typing
 from . import _jcustomizer
 
 
 __all__ = ['JArray']
 
 
-class JArray(_jpype._JObject, internal=True):  # type: ignore[call-arg]
+T = typing.TypeVar('T')
+
+
+class _JArrayGeneric(collections.abc.Sequence[T]):
+    
+    @abc.abstractmethod
+    def __setitem__(self, index, value):
+        ...
+
+
+if typing.TYPE_CHECKING:
+    _array_base = _JArrayGeneric
+else:
+    # NOTE: the subscript operator needs to be used in the class definition for typing
+    _array_base = {T : _jpype._JObject}
+
+
+class JArray(_array_base[T], internal=True):  # type: ignore[call-arg]
     """ Creates a Java array class for a Java type of a given dimension.
 
     This serves as a base type and factory for all Java array classes.
@@ -92,6 +112,18 @@ def __new__(cls, tp, dims=1):
     def of(cls, array, dtype=None):
         return _jpype.arrayFromBuffer(array, dtype)
 
+    def __class_getitem__(cls, key):
+        if key is _jpype.JClass:
+            # explicit check for JClass
+            # _toJavaClass cannot be used
+            # passing int, float, etc is not allowed
+            key = _jpype._java_lang_Class
+        if isinstance(key, (str, _jpype._java_lang_Class)):
+            key = _jpype.JClass(key)
+        if isinstance(key, _jpype.JClass):
+            return type(key[0])
+        raise TypeError("Cannot instantiate unspecified array type")
+
 
 class _JArrayProto(object):
 
@@ -104,6 +136,10 @@ def __iter__(self):
     def __reversed__(self):
         for elem in self[::-1]:
             yield elem
+    
+    def __contains__(self, item):
+        # "in" works without this but this should be more efficient
+        return _jpype.JClass("java.util.Arrays").asList(self).contains(item)
 
     def clone(self):
         """ Clone the Java array.
diff --git a/jpype/_jclass.py b/jpype/_jclass.py
index faa905f24..3a93c8a93 100644
--- a/jpype/_jclass.py
+++ b/jpype/_jclass.py
@@ -97,6 +97,11 @@ def __new__(cls, jc, loader=None, initialize=True):
 
         # Pass to class factory to create the type
         return _jpype._getClass(jc)
+    
+    @classmethod
+    def __class_getitem__(cls, index):
+        # enables JClass[1] to get a Class[]
+        return JClass("java.lang.Class")[index]
 
 
 class JInterface(_jpype._JObject, internal=True):  # type: ignore[call-arg]
diff --git a/native/python/pyjp_class.cpp b/native/python/pyjp_class.cpp
index fc633e11c..9fb4071a0 100644
--- a/native/python/pyjp_class.cpp
+++ b/native/python/pyjp_class.cpp
@@ -728,8 +728,9 @@ static PyObject *PyJPClass_array(PyJPClass *self, PyObject *item)
 
 	if (self->m_Class == NULL)
 	{
-		PyErr_Format(PyExc_TypeError, "Cannot instantiate unspecified array type");
-		return NULL;
+		PyObject *res = PyObject_CallMethod((PyObject *)self, "__class_getitem__", "O", item);
+		Py_DECREF(item);
+		return res;
 	}
 
 	if (PyIndex_Check(item))
diff --git a/test/jpypetest/test_array.py b/test/jpypetest/test_array.py
index 6f0c60855..011b56bf6 100644
--- a/test/jpypetest/test_array.py
+++ b/test/jpypetest/test_array.py
@@ -593,6 +593,7 @@ def testShortcut(self):
         # Check Objects
         self.assertEqual(JString[5].getClass(), JArray(JString)(5).getClass())
         self.assertEqual(JObject[5].getClass(), JArray(JObject)(5).getClass())
+        self.assertEqual(JClass[5].getClass(), JArray(JClass)(5).getClass())
 
         # Test multidimensional
         self.assertEqual(JDouble[5, 5].getClass(), JArray(JDouble, 2)(5).getClass())
@@ -601,3 +602,14 @@ def testShortcut(self):
     def testJArrayIndex(self):
         with self.assertRaises(TypeError):
             jpype.JArray[10]
+
+    def testJArrayGeneric(self):
+        self.assertEqual(type(JObject[0]), JArray(JObject))
+
+    def testJArrayGeneric_Init(self):
+        Arrays = JClass("java.util.Arrays")
+        self.assertTrue(Arrays.equals(JObject[0], JArray(JObject)(0)))
+
+    def testJArrayInvalidGeneric(self):
+        with self.assertRaises(TypeError):
+            jpype.JArray[object]