title: GWT:how to get the value of a checkbox of a cellTable
body: <p><img src="https://i.stack.imgur.com/N6Zo0.png" alt="enter image description here"></p>
  
  <p>I have this situation , i want to delete the  objects in this celltable whose checkbox is Check on the clik of this "Delete" Button , </p>
  
  <p>Any idea how to get those objects whose checkbox is checked in this cellTable, when i click the delte button ..</p>
  
  <p>Thanks </p>