Althought it is a commercial distribution, Redhat Enterprise Linux is only supplied with software that is considered to be free; that is, openly redistributable, with licences that meet the Open Source Institute's guidelines for being considered to be open source software.
Sun's Java Development Kit does not meet this guidelines; while the JDK is available for free download, its source is not available and there are restrictions on its use. Hence, for this reason, Sun's JDK is not supplied with Redhat Enterprise Linux.
This article provides a guide to building RPMs from Sun's JDK, so that they will work correctly with your system. The following instructions will also apply to anyone running Fedora.