If you receive File in Use. The action can't be completed because the file is open in another program even if file is closed in another program, see this.

The action can't be completed because the folder or a file in it is open in another program. Close the folder or file and try again. This is done for good reason.

If you're trying to delete a Mac app but can't because it's still open, don't worry! There are a few ways to fix this issue.