title: how to check if an excel file is password protected using jxl
body: <p>I am trying to write and read a password protected excel file, I found that I can set and reset a password by using "com.jexcel.util.ExcelAdapter" library. 
  But I could not find a method to check if file is protected.</p>
  
  <p>Can any one guide me? </p>
  
  <p>Thanks!</p>