I dont find how you can remove a column using the Apache POI API. I'd appreciate an example code or help about this point. Thanks

I believe you need to go lower each HSSFRow and call HSSFRow.getCell after which HSSFRow.removeCell. The API is oriented towards rows, instead of posts, and incredibly couple of procedures work on the entire column level.

Sample code (untested):

HSSFSheet sheet = ...
int colToRemove = 5;
Iterator rowIter = sheet.iterator();
while (rowIter.hasNext()) {
   HSSFRow row = (HSSFRow)rowIter.next();
   HSSFCell cell = row.getCell(colToRemove);
   row.removeCell(cell);
}