import java.math.BigInteger;

public class bytetohex {
    public static String toHexString(byte[] hash)
    {
        // Convert byte array into signum representation
        BigInteger number = new BigInteger(1, hash);

        // Convert message digest into hex value
        StringBuilder hexString = new StringBuilder(number.toString(16));

        // Pad with leading zeros
        while (hexString.length() < 64)
        {
            hexString.insert(0, '0');
        }

        return hexString.toString();
    }
}