Sun offers a "jdk-6u22-linux-ia64.bin" for download on their sites. But dev-java/sun-jdk does not support ia64. Please add it to the supported arches.
ia64 arch team is understaffed and unwilling to maintain Java support. Please refer to bug #345433 for discussion. If you plan to help the team maintain it please go ahead.
Can't find such a download for recent versions.
Closing this bug in favor of bug 349020 which is about adding ia64 support based on icedtea.