Java 7 first released in July 2011 brought a lot of anticipated innovations to the Java world. Users, for example, got a more powerful Java machine with improved protection against external threats, whereas developers got a bunch of new features from task paralleling with the help of the Fork/Join framework to syntactic sugar from Project Coin.
Over the last months it has become obvious that Java 7 popularity keeps growing. For instance, the Google search queries statistics by keywords shows that there have been more searches by Java 7 than by Java 6.
Last summer Oracle finally stated that starting from February 2013 Java 6 will not be supported. From now on, only customers who obtained a commercial license can get Oracle assistance and timely bug fixes.
Starting from Confluence 5, Atlassian also stops supporting Java 6 which leaves only Java 7 as a supported Java platform for Confluence. With this in mind, make sure you updated Java as well when updating your Confluence to version 5.0.