Add callback function to Java stream

Question

Let's say I want to perform the following operations:

• List the files in a given directory (as a stream)
• Map each file (Path) into a Reader (BufferedReader for example) for a consumer to consume.
• Once a file has been consumed, delete the files

The code would look a bit like this:

Stream<Reader> stream = Files.list(Paths.get("myFolder")) // Returns a stream of Path
  .callback(Files::delete)                                // This would have to be called after the reader has been consumed
  .map(Files::newBufferedReader);                         // Maps every path into a Reader

If I use peek() to delete the files, then the file won't be there when it needs to be mapped into a Reader, so I'd need something that runs after the stream is consumed. Any idea?

Answer 1

You can use the DELETE_ON_CLOSE option:

Stream<Reader> stream = Files.list(Paths.get("myFolder"))
        // TODO handle IOException
        .map(path -> Files.newInputStream(path, StandardOpenOption.DELETE_ON_CLOSE))
        .map(InputStreamReader::new)
        .map(BufferedReader::new);