fixes hashCode overflow. (disclamer: i wont talk about collision probabiliity or whatever. In my point of view, it seems very low, as the id() is based on the address of the object, it except if you uses tons of memory, you wont get it. And whatever the changes are, this will never keep up safe from colliding with others java object.). Closes #146

jnius/__init__.py

@@ -15,15 +15,17 @@ from .reflect import *
 # XXX monkey patch methods that cannot be in cython.
 # Cython doesn't allow to set new attribute on methods it compiled
 
+HASHCODE_MAX = 2 ** 31 - 1
+
 class PythonJavaClass_(PythonJavaClass):
 
     @java_method('()I', name='hashCode')
     def hashCode(self):
-        return id(self)
+        return id(self) % HASHCODE_MAX
 
     @java_method('()Ljava/lang/String;', name='hashCode')
     def hashCode_(self):
-        return '{}'.format(id(self))
+        return '{}'.format(self.hashCode())
 
     @java_method('()Ljava/lang/String;', name='toString')
     def toString(self):