You want to use:
git checkout --ours foo/bar.java
git add foo/bar.java
If you rebase a branch feature_x against main (i.e. running git rebase main while on branch feature_x), during rebasing ours refers to main and theirs to feature_x.
As pointed out in the git-rebase docs:
Note that a rebase merge works by replaying each commit from the working branch on top of the branch. Because of this, when a merge conflict happens, the side reported as ours is the so-far rebased series, starting with <upstream>, and theirs is the working branch. In other words, the sides are swapped.
For further details read this thread.