Java - Write code to get MD5 Hash for a string

Requirements

Write code to get MD5 Hash for a string
Demo

//package com.book2s;
import java.security.MessageDigest;

public class Main {
    public static void main(String[] argv) {
        String securityStr = "book2s.com";
        System.out.println(MD5(securityStr));
    }//from ww w  .jav  a 2  s .  c o  m

    public static String MD5(String securityStr) {
        char hexDigits[] = { '0', '1', '2', '3', '4', '5', '6', '7', '8',
                '9', 'A', 'B', 'C', 'D', 'E', 'F' };
        try {
            byte[] btInput = securityStr.getBytes();
            MessageDigest mdInst = MessageDigest.getInstance("MD5");
            mdInst.update(btInput);
            byte[] md = mdInst.digest();
            int j = md.length;
            char str[] = new char[j * 2];
            int k = 0;
            for (int i = 0; i < j; i++) {
                byte byte0 = md[i];
                str[k++] = hexDigits[byte0 >>> 4 & 0xf];
                str[k++] = hexDigits[byte0 & 0xf];
            }
            return new String(str).toLowerCase();
        } catch (Exception e) {
            e.printStackTrace();
            return null;
        }
    }
}