This week's book giveaway is in the OCAJP 8 forum. We're giving away four copies of OCA Java SE 8 Programmer I Study Guide and have Edward Finegan & Robert Liguori on-line! See this thread for details.
Trupti, If you are using a connection pool, close() returns the connection to the pool. If you are not using a connection pool, close() closes the connection.
close() does not null out the reference to the connection object in your code. If you try to use the connection, you will get a StaleConnectionException. However, having this reference does not affect the connection resources.