DataStore.java

import java.io.*;

public class DataStore {

    private static final String FILE = "bank.dat";

    public static void save(Bank bank) {
        try (ObjectOutputStream out =
                     new ObjectOutputStream(new FileOutputStream(FILE))) {
            out.writeObject(bank);
        } catch (IOException e) {
            System.out.println("Error saving data.");
        }
    }

    public static Bank load() {

        File file = new File(FILE);

        if (!file.exists())
            return new Bank();

        try (ObjectInputStream in =
                     new ObjectInputStream(new FileInputStream(FILE))) {
            return (Bank) in.readObject();
        } catch (Exception e) {
            return new Bank();
        }
    }
}