title: Ever need to destroy a singleton instance?
body: <p>By using a singleton, only one instance of it can be created. Do we ever need to destroy that instance?</p>
  
  <p>I have a singleton DBManager, which manages a JDBC connection and query operations. By calling its static newInstance method, I can get the instance of it, then I do some queries. Finally, I want to close the Database connection, and I call another static method close to close the JDBC connection.</p>
  
  <p>Now the connection has been closed, while the instance of DBManager is still alive but not useful. Do I need to destroy it by for example assigning it to null? Otherwise it may be referenced by mistake later on.</p>
  
  <p>If I assign that instance with null, then call newInstance method again, will I get another new different instance?  </p>