You can keep a long variable (to address 64 bit needs) in you java program.For example call it as

long cObjectID;

in your C/C++ code you can have funtion like the following

void  setCObjectId
(JNIEnv *env, jobject thisObject, jlong lCObjectId){

	jclass classzz = env->GetObjectClass(thisObject);
	jfieldID fid =env->GetFieldID(classzz,"cObjectID","J");
	env->SetLongField(thisObject,fid,lCObjectId);
	

}

which sets the pointer associated with you struct pointer which is passed through "lCObjectId".

You can have the additional method

jlong  getCObjectId
(JNIEnv *env, jobject thisObject){

	jclass classzz = env->GetObjectClass(thisObject);
	jfieldID fid =env->GetFieldID (classzz,"cObjectID","J");
	jlong id = env->GetLongField(thisObject,fid);
	return id;

}

to get the Pointer.

Similar to to this you can have a set and get in you java class to reference the pointer.