android md5

//MD5加密，32位  
        public static String MD5(String str)  
        {  
            MessageDigest md5 = null;  
            try  
            {  
                md5 = MessageDigest.getInstance("MD5"); 
            }catch(Exception e)  
            {  
                e.printStackTrace();  
                return "";  
            }  
              
            char[] charArray = str.toCharArray();  
            byte[] byteArray = new byte[charArray.length];  
              
            for(int i = 0; i < charArray.length; i++)  
            {  
                byteArray[i] = (byte)charArray[i];  
            }  
            byte[] md5Bytes = md5.digest(byteArray);  
              
            StringBuffer hexValue = new StringBuffer();  
            for( int i = 0; i < md5Bytes.length; i++)  
            {  
                int val = ((int)md5Bytes[i])&0xff;  
                if(val < 16)  
                {  
                    hexValue.append("0");  
                }  
                hexValue.append(Integer.toHexString(val));  
            }  
            return hexValue.toString();  
        }