How to calculate hash value of a file in Java? [duplicate]

Answer 1

You can read the file and calculate the value of the hash as you go.

    byte[] buffer= new byte[8192];
    int count;
    MessageDigest digest = MessageDigest.getInstance("SHA-256");
    BufferedInputStream bis = new BufferedInputStream(new FileInputStream(fileName));
    while ((count = bis.read(buffer)) > 0) {
        digest.update(buffer, 0, count);
    }
    bis.close();

    byte[] hash = digest.digest();
    System.out.println(new BASE64Encoder().encode(hash));

This doesn't assume anything about character sets or about the file fitting into memory, and it doesn't ignore line terminators either.

Or you can use a DigestInputStream.