* retention practices, once the resulting connection is disconnected, the given ones
* will no longer be referenced and hence will only have their {@code disconnect} method
* called once (via the returned object).
*/
public static Connection join (final Connection... connections) {
return new Connection() {
@Override public void disconnect () {
if (_conns == null) return;
for (Connection conn : _conns) conn.disconnect();
_conns = null;
}