Java-读写BIN文件中的数组

Question

I am working on a small library application which stores technical manuals in this format:

Currently, I am trying to enable the contents of the library to be saved and loaded on demand by the user, to a bin file.

However when I try and load a library file, the only change is that "-1" is printed to the console. Shown here:

Ideally I would like this to store the loaded manuals into the users current library.

Here is my code:

//Choice 7: Load Library:

            if(Menu.menuChoice == 7){
                boolean loadYesNo = Console.readYesNo("\n\nThe manualKeeper app is able to load and display any 'Library.txt' files \nfound in your home folder directory.\n\nWould you like to load and display library? (Y/N):\n");
                String fileName = "Library.bin";
                if(loadYesNo==true){
                try {
                    FileInputStream fileIs = new FileInputStream(fileName);
                    ObjectInputStream is = new ObjectInputStream(fileIs);
                    Object x = is.read();
                    System.out.println(x);
                    is.close();
                } catch (FileNotFoundException e) {
                    e.printStackTrace();
                } catch (IOException e) {
                    e.printStackTrace();
                }
                Menu.displayMenu();
                }
                else if(loadYesNo==false){
                    System.out.println("\n\n--------------------------------------------------------------------------");
                    System.out.println("\n                             Library not loaded!\n");
                    System.out.println("--------------------------------------------------------------------------\n");
                    Menu.displayMenu();
                }
            }

//Choice 0: Exit the program:

            if(Menu.menuChoice == 0){
                if(Menu.menuChoice == 0){
                    if(Library.ManualList.size() > 0){
                        boolean saveYesNo = Console.readYesNo("\nThe manualKeeper app is able to save your current library to a '.txt' \nfile in your home folder directory (C:\\Users\\ 'YOUR NAME').\n\nWould you like to save the current library? (Y/N):\n");
                        String fileName = "Library.bin";
                        if(saveYesNo==true){
                            try {
                                FileOutputStream fileOs = new FileOutputStream(fileName);
                                ObjectOutputStream os = new ObjectOutputStream(fileOs);
                                for (int i = 0; i < Library.ManualList.size(); i++){
                                    os.writeObject(Library.ManualList.get(i).displayManual());
                                    os.close();
                                }
                            } catch (FileNotFoundException e) {
                                e.printStackTrace();
                            } catch (IOException e) {
                                e.printStackTrace();
                            }
                            System.out.println("DONE WRITING!");
                        }
                            else if(saveYesNo==false){
                                System.out.println("\n\n--------------------------------------------------------------------------");
                                System.out.println("\n                              Library not saved!\n");
                                System.out.println("--------------------------------------------------------------------------\n");
                                break exit;
                        }
                        Menu.displayMenu();
                    }else if(Library.ManualList.isEmpty()){ 
                        Menu.displayMenu();
                    }
                }
            }               

        }
    System.out.println("\n              ~   You have exited the manualKeeper app!   ~                  ");
    System.out.println("\n                  Developed by Oscar Moore - 2014 - UWL\n");
    System.out.println("\n                                   <3\n");

}
}

If more code needs to be shown please let me know. Thank you.

Answer 1

The lines:

Object x = is.read(); System.out.println(x);

are resulting in the -1 you're seeing in the console.

From the javadocs ( link ), read() returns:

-1 if the end of the stream is reached.

So, first, check that Library.bin is being saved correctly (use a text editor after saving).

Then, make sure the file you are reading in is the same exact file.

It looks like you aren't using a full path to the file. eg Library.bin versus /home/project/Library.bin . Try using the full path. I suspect that is the problem.