To circumvent a conflicting files issue, manual intervention is required only if package java-common is installed. This can be checked with the following command:
$ pacman -Q java-common
java-common ...
If so, please run the following prior to upgrading:
# archlinux-java unset
# pacman -Sydd --asdeps java-runtime-common
:: java-runtime-common and java-common are in conflict. Remove java-common? [y/N] y
# archlinux-java fix
You can then go ahead and upgrade:
# pacman -Su
Please note that new package java-runtime-common does not use nor support forcing JAVA_HOME as former package java-common did. See the Java wiki page for more info.