A database resource in the java.sql package that is opened but not closed may cause a resource leak and ultimately resource exhaustion.

Ensure that the resource is always closed to avoid a resource leak. Note that, because of exceptions, it is safest to close a resource in a finally block.

For Java 7 or later, the recommended way to close resources that implement java.lang.AutoCloseable is to declare them within a try-with-resources statement, so that they are closed implicitly.

In the following example, the resources stmt and rs are opened but not closed.

In the following example, the resources stmt and rs are declared within a try-with-resources block and are thus closed implicitly.

Note that the Connection that is passed into the method is a long-lived object that was created elsewhere and therefore need not be closed locally. It should instead be closed by the code that created it or by a server shutdown procedure, as appropriate.
  • IBM developerWorks: Java theory and practice: Good housekeeping practices.
  • The Java Tutorials: The try-with-resources Statement.