Using hg revert in Mercurial
As other's have pointed out, you can safely delete these files.
You can remove them by executing this command from the root of your repo:
rm `hg st -un | grep orig`
If you want to revert, and don't care at all about backing up the original files, the command you want is:
hg update -C
I find the purge extension handy. Usage:
hg purge
"This extension purges all files and directories not being tracked by Mercurial"
...including the .orig files but excluding ignored files (unless you use --all).
Yes, you can delete them. It's a safety feature in case you reverted something you didn't mean to revert.
You can also use the flag --no-backup and the .orig files will not be created
hg revert --no-backup filename.java
As of Mercurial 2.0, you can instead use the flag -C to supress the .orig files from being created
hg revert -C filename.java