File paths can be absolute or relative. If they are absolute, they fully specify where the file is. If they are relative, they specify it in relation to the current working directory (system property "user.dir").
If neither of these suits you, then you have a problem. It is possible to read directories in
Java, and hence to search a tree of directories for a file with a particular name. However, if there are a lot of directories to search, it will take a long time.