The C++ destructor is not a way to destruct objects - it's a set of operation that are to be done when the object is destructed. In Java you have no control on the time when objects are destructed (they may be even never destructed), so putting any important code to be executed at object destruction is strongly discouraged (although possible - finalize method). If you ask not for a destructor but for a way to explicitly destroy given object, you are inviting dangling references into your code. They are not welcome.
