public String insertFile(File file) throws SQLException {
   String newName = file.getName() + "_" + (this.getFileLastID() + 1);
   if (isFriend(file.getSender(), file.getReceiver())
       && !existFile(file)) { // Check if the sender and receiver are friends
     try {
       // creates a SQL Statement object in order to execute the SQL insert command
       stmt = conn.createStatement();
       stmt.execute(
           "INSERT INTO Files (Filename, Size, Sender, Receiver, DateUpload, TimeUpload ) "
               + "VALUES ('"
               + newName
               + "', "
               + (int) file.length()
               + ", "
               + getProfileID(file.getSender())
               + ", "
               + getProfileID(file.getReceiver())
               + ", '"
               + file.getDateUpload()
               + "' , '"
               + file.getTimeUpload()
               + "')");
       stmt.close();
       // System.out.println("Requête executée");
     } catch (SQLException e) {
       // System.err.println(e.toString());
       e.toString();
       throw e;
     }
     return newName;
   } else {
     return null;
   }
 }
 public boolean existFile(File file) {
   boolean res = false;
   int senderID = this.getProfileID(file.getSender());
   int receiverID = this.getProfileID(file.getReceiver());
   if (senderID != -1 && receiverID != -1) {
     try {
       // creates a SQL Statement object in order to execute the SQL insert command
       stmt = conn.createStatement();
       ResultSet result =
           stmt.executeQuery(
               "SELECT * FROM FILES WHERE Size="
                   + (int) file.length()
                   + " AND Sender="
                   + senderID
                   + " AND Receiver="
                   + receiverID
                   + " AND Filename LIKE '"
                   + file.getName()
                   + "%'");
       if (result.next()) {
         res = true;
       }
     } catch (SQLException ex) {
       Logger.getLogger(DataService.class.getName()).log(Level.SEVERE, null, ex);
     }
   }
   return res;
 }