java - Replace a certain String with iText TextField in ListArray -

using of itext want create pdf document containing table values file db. next step, before putting values table want find values matching pre-defined keyword , replace them textfields. thus, text fields should in appropriate cells, i.e. if keyword @ 2nd row , 3rd column, cell should text field inserted. perform wrote following method:

try {     scanner scan = new scanner(new file("filedb.txt"));     scan.usedelimiter(",|" + system.getproperty("line.separator"));      int = 0;     while(scan.hasnext()) {         string t1 = scan.next();         string t2 = scan.next();         string t3 = scan.next();         string t4 = scan.next();          // puts columns arraylist         list<object> allcolumns = new arraylist<object>();         allcolumns.add(t1);         allcolumns.add(t2);         allcolumns.add(t3);          // *updated* checks 'keywrd' in columns , replaces them txt_fld         (int n=0; n < allcolumns.size(); n++) {             pdfpcell cell = new pdfpcell();             cell.setcellevent(new textfields(n));              if (allcolumns.get(n).equals("keywrd")) {                 allcolumns.set(n, cell);             }         }          // inserts columns table cells          (pdfpcell values : allcolumns) {             table.addcell(values);         }          // creates textfields @ last column of given table         pdfpcell cell = new pdfpcell();         cell.setcellevent(new textfields(i));         table.addcell(cell);         i++;     }     scan.close();  } catch (exception e) {     e.printstacktrace(); } 

error:

the method add(pdfpcell) in type list not applicable arguments (object)

how adapt above structure code in order perform replace method according keyword?