Como saber se um objeto ainda está sendo referenciado?

public class ConexaoDB {
   private static ConexaoDB myInstance = null;

   private Connection conn = null;
   private String user;
   private String password;
   private String db;
   private String port;
   private static String IP;

   private ConexaoDB() {
      try {
         Class.forName("oracle.jdbc.OracleDriver");
         conn = DriverManager.getConnection("jdbc:oracle:thin:" + user + "/" + password + "@" + IP + ":" + port + ":" + db);
      } catch (SQLException sqle) {
         sqle.printStackTrace();
      } catch (ClassNotFoundException cnfe) {
         cnfe.printStackTrace();
      } // try
   }
 	
   public synchronized static ConexaoDB getInstance() {
      if (conn == null) {
         conn = new ConexaoDB();
      }
      return conn;
   }

   //Demais getters
 }