Java file hash for identifying identical files

Question

I would like to get the hash of files (mostly video files) independent of external properties such as path and file name. I'll be needing to store hash in a database and compare file hash to find identical files.

You can make a hash function depend on anything you like, including 'external properties' or not. What is it about writing such a function that you don't understand? — DJClayworth
– DJClayworth, Commented Apr 29, 2011 at 15:47

Rakim · Accepted Answer · 2015-11-21 21:47:49Z

5

Have a look at the DigestInputStream class: http://docs.oracle.com/javase/7/docs/api/java/security/DigestInputStream.html

edited Nov 21, 2015 at 21:47

Rakim

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answered Apr 29, 2011 at 15:47

Brigham

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Clint · Accepted Answer · 2011-04-29 16:03:53Z

2

public byte[] digestFile( File f ){
  try {
    MessageDigest messageDigest = MessageDigest.getInstance("SHA-1");
    FileInputStream fis = new FileInputStream( f );
    byte[] buffer = new byte[1024];
    int read = -1;
    while ((read = fis.read(buffer)) != -1) {
      messageDigest.digest(buffer, 0, read);
    }
    return messageDigest.digest();
  } catch (VariousExceptions e) {
    //handle
  }
}

answered Apr 29, 2011 at 16:03

Clint

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Comments

ColinD · Accepted Answer · 2011-04-29 16:47:45Z

1

Depending on what you need, you can do this pretty easily using Guava's Files and ByteStreams classes:

byte[] digest = Files.getDigest(file, MessageDigest.getInstance("SHA"));

edited Apr 29, 2011 at 16:47

answered Apr 29, 2011 at 16:06

ColinD

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