how can i check if files exist for the given list of paths?
file, file-io, guava, java
Solution
The creation of 50,000 `File` objects is almost certainly not the bottleneck. The actual filesystem operations is probably what's making it slow.
I have two suggestions:
- Before checking, sort paths by their location to make best use of filesystem caches.
- If a sub-directory does not exist, you can automatically assume that all files and sub-directories therein don't exist either.
Problem
I have a list of 50,000 paths and I need to check if a file exists against each of these paths. Right now, I am verifying each path independently like this: ``` public static List<String> filesExist(String baseDirectory, Iterable<String> paths) throws FileNotFoundException{ File directory = new File(baseDirectory); if(!directory.exists()){ throw new FileNotFoundException("No Directory found: " + baseDirectory ); }else{ if(!directory.isDirectory()) throw new FileNotFoundException(baseDirectory + " is not a directory!"); } List<String> filesNotFound = new ArrayList<String>(); for (String path : paths) { if(!new File(baseDirectory + path).isFile()) filesNotFound.add(path); } return filesNotFound; } ``` Is there a way to improve it so that I don't create 50,000 File objects ? I am also using guava. Is there any utility in there which can help me with bulk `exists()` method ?