当用户正在阅读PDF并完成阅读此文件并关闭PDF时，我需要保存用户在使用PDFBox库2.0.20关闭PDF之前阅读的最后一页

try {
      InputStream bos = new ByteArrayInputStream(lib.getPdf()); // lib.getPdf returns the pdf file in byte[] array.
      int tamañoPDF= bos.available();
      byte [] datosPDF = new byte [tamañoPDF];
      bos.read(datosPDF, 0 , tamañoPDF);
      OutputStream out = new FileOutputStream (button.getText());
      out.write(datosPDF);
      button.addActionListener(new ActionListener(){ //setting an action to a button.
      public void actionPerformed(ActionEvent ae)
        {try {
            Desktop.getDesktop().open(new File(button.getText())); //the pdf is opened
            out.close(); //here I think I have to insert the code that save the page number
            } catch (IOException ex) {
                            Logger.getLogger(InfoDelLibro.class.getName()).log(Level.SEVERE, null, ex);
                        }

                    }
          });

    } catch (IOException ex) {
         Logger.getLogger(InfoDelLibro.class.getName()).log(Level.SEVERE, null, ex);
    }

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