digest.java

import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
import java.io.UnsupportedEncodingException;
import java.security.*;


public class HelloWorld {

     public static void main(String []args) 
     throws UnsupportedEncodingException, NoSuchAlgorithmException {
        String[] codes = {"ONE", "TWO"}; 
        String digest = verification_digest("ef591fbbc527d77402d9a10dba92c195", "purchase", 
            "812881", "developer@example.com", "200.00", "2014-01-01T00:00:00+00:00", 
            codes);
        System.out.println(digest);
     }
     
    public static String verification_digest(String key, String event_category, 
        String event_number, String email, String subtotal, 
        String order_date, String[] coupons) 
    throws UnsupportedEncodingException, NoSuchAlgorithmException {
        String string = key + "|" + event_category + "|" + 
            event_number + "|" + email + "|" + (subtotal != null ? subtotal : "") + "|" + 
            (order_date != null ? order_date : "") + "|" + strJoin(coupons, ",");
        string = string.replaceAll("\\|\\|", "|").replaceAll("\\|$", "");
        System.out.println(string);

        return hash256(string);
        
    }
    public static String strJoin(String[] aArr, String sSep) {
        StringBuilder sbStr = new StringBuilder();
        for (int i = 0, il = aArr.length; i < il; i++) {
            if (i > 0)
                sbStr.append(sSep);
            sbStr.append(aArr[i]);
        }
        return sbStr.toString();
    }
    public static String hash256(String data) throws NoSuchAlgorithmException {
        MessageDigest md = MessageDigest.getInstance("SHA-256");
        md.update(data.getBytes());
        return bytesToHex(md.digest());
    }
    public static String bytesToHex(byte[] bytes) {
        StringBuffer result = new StringBuffer();
        for (byte byt : bytes) result.append(Integer.toString((byt & 0xff) + 0x100, 16).substring(1));
        return result.toString();
    }
}