EXCEPTION STREAMCORRUPTED

[hollow jungle]

Hi so my code is this

public static void main(String[] args) throws IOException, ClassNotFoundException {

        char opc;
        do {
            System.out.println("1- Agregar contactos\n2- Modificar contacto\n3- Mostrar\n4- Salir");
            opc = in.nextLine().charAt(0);

            switch (opc) {
            case '1':
                agregarContacto();
                break;

            case '2':
                modificarContacto();
                break;

            case '3':
                mostrarContactos();
            }

        } while (opc != '4');
    }

    public static void agregarContacto() throws IOException {
        FileOutputStream fos = new FileOutputStream(fichero, true);
        ObjectOutputStream oos = new ObjectOutputStream(fos);

        for (int i = 0; i < 4; i++) {
            System.out.println("Introduce " + textoParaMostrar[i]);
            textoAGuardar[i] = in.nextLine();
        }

        Persona nuevoContacto = new Persona(textoAGuardar[0], textoAGuardar[1], textoAGuardar[2], textoAGuardar[3]);

        oos.writeObject(nuevoContacto);
        oos.flush();
    }
    public static void mostrarContactos() throws IOException, ClassNotFoundException {
        
        if (fichero.exists()) {
                FileInputStream fis = new FileInputStream(fichero);
                ObjectInputStream ois = new ObjectInputStream(fis);
                while (true) {
                    try {
                        Persona p = (Persona) ois.readObject();
                        System.out.println(p.toString());
                    } catch (EOFException e) {
                        break;
                    }
                }

                ois.close(); // Cierra el ObjectInputStream después de leer todos los contactos
        } else {
            System.out.println("El archivo no existe o no hay contactos almacenados.");
        }
    }

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[hollow jungle]

So the thing im doing is, Im creating an object of type Person everytime I mark 1 and that object saves in a file serelizated because I have another Class which is called Person and there I implemented the Serializable, so the THING is when I want to read all the objetcs, which means deserenize them it comes an exception into my screem.
I dont get why if Im doing corrently as far as I know by my self.

Any help is welcome, Thanks!!!!!!!

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[random brook]

could you share the stacktrace

[hollow jungle]

wdym?

do u want me to send u both classes?

[random brook]

the error. Please send the full error

[hollow jungle]

ohhh

yes

java.io.StreamCorruptedException: invalid type code: AC
at java.base/java.io.ObjectInputStream.readObject0(ObjectInputStream.java:1764)
at java.base/java.io.ObjectInputStream.readObject(ObjectInputStream.java:509)
at java.base/java.io.ObjectInputStream.readObject(ObjectInputStream.java:467)
at clase/agendaobjetos.Main.mostrarContactos(Main.java:83)
at clase/agendaobjetos.Main.main(Main.java:40)
1- Agregar contactos

@random brook

**java.io.StreamCorruptedException: invalid type code: AC
at **

[random brook]

how many ObjectOutputStreams do you create ?

[hollow jungle]

You see them here @random brook

I created one

Inside the method to create a person:
1 FileOutputStream
1 ObjectOutputStream

Inside the method to show all the persons:
1 FileInputStream
1 ObjectInputStream

[random brook]

I see. You can't use the append option with an ObjectOutputStream. It will write its header to the file again causing the ObjectInputStream to throw said error.

I'd also recommend creating a simple CSV file instead of using ObjectOutputStream if you are just looking for a way to store the information of a Person in a file.

[hollow jungle]

What do you mean, I dont get what you are saying

[random brook]

FileOutputStream fos = new FileOutputStream(fichero, true); You are creating a FileOutputStream with the append option set. This won't work in combination with a ObjectOutputStream remove the boolean in the constructor.

[hollow jungle]

Okay so now it shows it, but it only shows the latest person created

It does not show all the objects I created as person

[random brook]

are you reading the person from a file every time you are querying them ?

[hollow jungle]

No, I want to read all the persons whenever I use the method mostrar()

not everytime I create one person I show it, thats not what I want

[random brook]

are you not allowed to hold the created objects in memory using an ArrayList ?

[hollow jungle]

yes I am

[random brook]

then use an arraylist and once the program terminates, write all person objects to the file. On program start up read from said file to load the saved Person objects

[hollow jungle]

wait, so I create the ArrayList, I insert persons into the arrayList but do I also need to have oos.writeObject(nuevoContacto); everytime I insert 1 person or just in the end I put oos.writeObject( and here the arraylist with all persons );

[random brook]

no. You don't write anything to the file while the program is running. When the user inputs 4 (he wants to terminate the program) then you write all objects stored in the arraylist to a file with an ObjectOutputStream. When you start the program the first thing you do is load all objects from the file using an ObjectInputStream

[hollow jungle]

But I have everything inside a do-while loop, so the program only ends when you choose to exit which means option 4. At no point I want the program to end when inserting several persons. What I want to do is insert 2-3 persons and then press the option 3, which is the option to display them in the screen

[random brook]

exactly. and when you press 3 you don't read the objects from a file but straight from the arraylist

[hollow jungle]

but I need to use the ois.readObject()

[random brook]

#Program start
read Person objects from File, store them in an ArrayList:
normal Program execution
write all Person objects from the ArrayList to the file
#Program end

[random brook]

you'll read from the file when you start the program

[hollow jungle]

okay so here I modified this as

public static void agregarContacto() throws IOException {
        
        FileOutputStream fos = new FileOutputStream(fichero);
        ObjectOutputStream oos = new ObjectOutputStream(fos);

        for (int i = 0; i < 4; i++) {
            System.out.println("Introduce " + textoParaMostrar[i]);
            textoAGuardar[i] = in.nextLine();
        }

        // Crea un nuevo objeto Persona con los datos proporcionados
        Persona nuevoContacto = new Persona(textoAGuardar[0], textoAGuardar[1], textoAGuardar[2], textoAGuardar[3]);
        contactos.add(nuevoContacto);

}

that method add every person into the arraylist

with the implicit method .add of the arraylist

so we put the case I add 3 persons, ifw

[random brook]

alright lastly get rid of these two lines:

        FileOutputStream fos = new FileOutputStream(fichero);
        ObjectOutputStream oos = new ObjectOutputStream(fos);

[hollow jungle]

okayokay

[hollow jungle]

so now for example, if I want to show those 3 persons I created how can I read them

theyre inside my arraylist

but Im obligated to use the method ois.readObject()

[random brook]

you loop over the list (either a traditional for loop or a for-each loop) and print each person object

[random brook]

this is the logical flow of your program

[hollow jungle]

I mean yea if I do

public void mostrarContactos() {
        for (Persona contacto : contactos) { //contactos is the name of the arraylist
            System.out.println(contacto);
        }
}

Of course it will show it

but thats not what I want

what I want is to Serializate into a file and then show it

[random brook]

You should create two methods:

public static ArrayList<Person> loadObjects() {
  //...
}

public static void saveObjects(ArrayList<Person> list) {
  //...
}

and they should be called like so:

public static void main(String[] args) {
    ArrayList<Person> persons =  loadObjects();
    do {  
        //...
    }while(opc != 4);
    saveObjects(persons);
}

[hollow jungle]

but there im not using the ObjectOutputStream guardarContactos = new ObjectOutputStream(new FileOutputStream(archivo))

and I need to use it

thats the examples it shows

[random brook]

the code needs to be filled in by you of course.

the code for writing to the file should be in saveObjects() and the code for reading from the file should be in loadObjects()

[hollow jungle]

why the first method has to return something?

[random brook]

because you want to read the Person objects from the file and preferably do something with them.

let's say you saved two Person objects in the file. When start the program you want both of these objects to be displayed if you print all known Person objects. If that first method doesn't return anything you can't display both objects.

[hollow jungle]

I did it

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[hollow jungle]

@random brook ty

anyways!