Connections, streams, files, and other classes that implement the ``Closeable`` interface or its super-interface, ``AutoCloseable``, needs to be closed after use. Further, that ``close`` call must be made in a ``finally`` block otherwise an exception could keep the call from being made. Preferably, when class implements ``AutoCloseable``, resource should be created using "try-with-resources" pattern and will be closed automatically.
Failure to properly close resources will result in a resource leak which could bring first the application and then perhaps the box the application is on to their knees.
