title: How to show a message over leading selection cell in JTable?
body: <p>I have a <code>JTable</code> with a custom <code>ListSelectionModel</code>, which contains a custom selection mode. This selection mode ensures that a selection is only made in one row, but with multiple cells. When a user clicks selects some cells in the table, the selected cells are all in the same row as the first selected cell. </p>
  
  <p>Now I want to create a small message above the upper-right corner of the leading selection cell, which displays some data, i.e. the count of the selected cells. The message should be moved when the leading selection is changed.</p>
  
  <p>But how do I do that? It is not a Tooltip as it is intended to be shown when user clicks into the table and selects cells and not by hovering over it.</p>
  
  <p>Any suggestions?</p>
  
  <p>best regards,
  htz</p>