"Generic" JArray support

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(

jpype/_jarray.py

@@ -92,6 +92,18 @@ 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 +116,10 @@ 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.

jpype/_jarray.pyi

@@ -0,0 +1,43 @@
+# *****************************************************************************
+#
+#   Licensed under the Apache License, Version 2.0 (the "License");
+#   you may not use this file except in compliance with the License.
+#   You may obtain a copy of the License at
+#
+#       http://www.apache.org/licenses/LICENSE-2.0
+#
+#   Unless required by applicable law or agreed to in writing, software
+#   distributed under the License is distributed on an "AS IS" BASIS,
+#   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+#   See the License for the specific language governing permissions and
+#   limitations under the License.
+#
+#   See NOTICE file for details.
+#
+# *****************************************************************************
+import abc
+import collections.abc
+import typing
+
+
+__all__ = ['JArray']
+
+
+T = typing.TypeVar('T')
+
+
+class _JArrayGeneric(collections.abc.Sequence[T]):
+
+    @abc.abstractmethod
+    def __setitem__(self, index, value):
+        ...
+
+
+class JArray(_JArrayGeneric[T], metaclass=abc.ABCMeta):
+
+    def __new__(cls, tp, dims=1):
+        ...
+
+    @classmethod
+    def of(cls, array, dtype=None):
+        ...

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]

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))

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]