Return null when file is missing or empty

Question

I'm using this code to get some HDD data from Linux:

public void getHDDInfo() throws IOException
    {
        try (DirectoryStream<Path> ds = Files.newDirectoryStream(Paths.get("/sys/block"), "sd*"))
        {
            // Get HDD Model
            StreamSupport.stream(ds.spliterator(), false)
                .map(p -> p.resolve("device/model")).flatMap(wrap(Files::lines))

        }
        try (DirectoryStream<Path> ds = Files.newDirectoryStream(Paths.get("/sys/block"), "sd*"))
        {
            // Get HDD Vendor
            StreamSupport.stream(ds.spliterator(), false)
                .map(p -> p.resolve("device/vendor")).flatMap(wrap(Files::lines))

        }
        try (DirectoryStream<Path> ds = Files.newDirectoryStream(Paths.get("/sys/block"), "sd*"))
        {
            // Get HDD State
            StreamSupport.stream(ds.spliterator(), false)
                .map(p -> p.resolve("device/state")).flatMap(wrap(Files::lines))
                .forEach(System.out::println);
        }
        try (DirectoryStream<Path> ds = Files.newDirectoryStream(Paths.get("/sys/block"), "sd*"))
        {
            // Get HDD Revision
            StreamSupport.stream(ds.spliterator(), false)
                .map(p -> p.resolve("device/rev")).flatMap(wrap(Files::lines))
                .forEach(System.out::println);
        }
        try (DirectoryStream<Path> ds = Files.newDirectoryStream(Paths.get("/sys/block"), "sd*"))
        {
            // Get HDD SCSI Level
            StreamSupport.stream(ds.spliterator(), false)
                .map(p -> p.resolve("device/scsi_level")).flatMap(wrap(Files::lines))
                .forEach(System.out::println);
        }
        try (DirectoryStream<Path> ds = Files.newDirectoryStream(Paths.get("/sys/block"), "sd*"))
        {
            // Get HDD SCSI is removable
            StreamSupport.stream(ds.spliterator(), false)
                .map(p -> p.resolve("device/removable")).flatMap(wrap(Files::lines))
                .forEach(System.out::println);
        }
        try (DirectoryStream<Path> ds = Files.newDirectoryStream(Paths.get("/sys/block"), "sd*"))
        {
            // Get HDD SCSI Level
            StreamSupport.stream(ds.spliterator(), false)
                .map(p -> p.resolve("device/size")).flatMap(wrap(Files::lines))
                .forEach(System.out::println);
        }
    }

But sometimes not all files are available or some of them are empty. Then I get this exception:

java.nio.file.NoSuchFileException: \sys\block

I there a way to modify the code to return null when there is no such file or the file is empty?

You need to check the file/directory exists first. – Peter Lawrey Aug 18 '14 at 13:42 — Peter Lawrey, Aug 18 '14 at 13:42
Can you show me some example? – Peter Penzov Aug 18 '14 at 13:43 — Peter Penzov, Aug 18 '14 at 13:43
Check with `Files.exists()` – Wundwin Born Aug 18 '14 at 13:48 — Wundwin Born, Aug 18 '14 at 13:48

score 5 · Answer 1 · answered Aug 18 '14 at 13:43

5

This should handle the cases where files don't exist:

try {
  // most of your stuff
}
catch (NoSuchFileException ex) {
  return null;
}

answered Aug 18 '14 at 13:43

Drux

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Is there any other better way to do this? – Peter Penzov Aug 18 '14 at 13:53
@PeterPenzov Better in what respect? – Drux Aug 18 '14 at 14:02
can you show me some example with code which checks file without exception? – Peter Penzov Aug 18 '14 at 14:05
@PeterPenzov http://stackoverflow.com/questions/1816673/how-do-i-check-if-a-file-exists-java-on-windows – Drux Aug 18 '14 at 14:06

Return null when file is missing or empty

1 Answers1