At the release of JIRA 6.0, due towards the middle of 2013, we are ending support for Java 6 (JRE and JDK 1.6).
Please note that Oracle has announced the end of public updates for Java 6: Java SE 6 End of Public Updates Notice.
You can stay on older versions of JIRA to support your existing Java installation. However, Atlassian will no longer fix bugs related to Java 6 (JRE and JDK 1.6) past the support end date. We are committed to helping our customers understand this decision and to assist you in upgrading JIRA, (we recommend the JIRA Installer for the upcoming 6.0 release, which will bundle its own Java 7 environment).
For more details about the announcement, please refer to this page: