Java: How to create SHA-1 for a file?

Question

What is the best way to create a SHA-1 for a very large file in pure Java6? How to implement this method:

public abstract String createSha1(java.io.File file         


        

Answer 1

public static String computeFileSHA1( File file ) throws IOException
{
    String sha1 = null;
    MessageDigest digest;
    try
    {
        digest = MessageDigest.getInstance( "SHA-1" );
    }
    catch ( NoSuchAlgorithmException e1 )
    {
        throw new IOException( "Impossible to get SHA-1 digester", e1 );
    }
    try (InputStream input = new FileInputStream( file );
         DigestInputStream digestStream = new DigestInputStream( input, digest ) )
    {
        while(digestStream.read() != -1){
            // read file stream without buffer
        }
        MessageDigest msgDigest = digestStream.getMessageDigest();
        sha1 = new HexBinaryAdapter().marshal( msgDigest.digest() );
    }
    return sha1;
}