the imports needed:

import java.util.logging.Logger;
import java.util.logging.Level;
import java.io.IOException;
import java.io.ObjectOutputStream;
import java.io.FileOutputStream;
import java.io.FileNotFoundException;

the code that write the file:

protected void kiirFajlba(List list, String fn) throws IOException {
        try (ObjectOutputStream oos = new ObjectOutputStream(new FileOutputStream(fn))) {
            oos.writeObject(list);
        } catch (FileNotFoundException ex) {
            Logger.getLogger(Asztal.class.getName()).log(Level.SEVERE, null, ex);
        }

    }

and the method that gives the datas:

 private void italokFajlban() throws IOException {

        this.kiirFajlba(italok, "italok.bin");

    }

italok here is an arayylist. quaston is this is good and if yes how i can reed in it gui. Thanks

that i show before, the big question is gui reading here.