为什么我的程序在序列化期间会覆盖以前添加的帐户？

Question

//我的程序用于序列化和反序列化当前帐户的对象。它成功地读取和写入数据，但是当我再次重新运行程序时。最后写的对象是唯一出现的对象。有什么方法可以更改此代码，以便它写入每个对象并再次读回每个对象。我需要序列化整个arrayList，如果是这样，我该怎么做？这是我的代码。

package ie.lyit.bank;
import java.util.ArrayList;
import java.io.*;
import java.util.Scanner;

public class CurrentFileHandler implements Serializable
{
    // Set up ArrayList to store currentAccount Objects
        private ArrayList<Current> currentAcc;

        // Set up default constructor
        public CurrentFileHandler()
        {
            // Construct currentAcc ArrayList
            currentAcc = new ArrayList<Current>();
        }   

        /** An Add method that creates an account, reads details of an account
         * and adds the account object to the ArrayList 
        **/
        public void add()
        {   // Create a currentAcc Object
            Current current = new Current();

            // Read its details
            current.read();

            // Add account to the ArrayList
            currentAcc.add(current);
            WriteRecordsToFile(current);
        }

        // A view method to allow a user to view an account
        public Current view()
        {
            System.out.println("Enter the account number for the account you wish to view: ");
            Scanner keyboardIn = new Scanner(System.in);

            // Read the account number of the account to be viewed from the user
            int accToView = keyboardIn.nextInt();

            // for every account object in currentAcc
            for(Current tmpCurrent: currentAcc)
            {
                // if it's number equals the number of accToView
                if(tmpCurrent.getAccountNo() == accToView)
            {
                // Display it
                System.out.println(tmpCurrent);
                return tmpCurrent;
            }
        }

            //  Account not found, return null
            System.out.println("Account Not Found.");
                return null;
        }

        // A list method to allow a user to list the account(s) 
        public void list()
        {
            // Loop through the ArrayList 
            for(Current tmpCurrent: currentAcc)
            // Display each account object 
            System.out.println(tmpCurrent);
        }

        // An Edit method to allow the user to view an account that they want to edit
        public void edit()
        {
            // Call view() to find, display and return the account to be edited
            Current tmpCurrent = view();
            // if the account was !null, i.e. it was found
            if(tmpCurrent != null)
            {
                // get it's index
                int index = currentAcc.indexOf(tmpCurrent);
                // Read in a new account and...
                tmpCurrent.read();
                // Reset it in the ArrayList
                currentAcc.set(index, tmpCurrent);
            }
        }
                // Delete method to allow the user to delete an account from the ArrayList
                public void delete()
                {
                    // Call view() to find, display and return the account to be deleted 
                    Current tmpCurrent = view();
                    // if the account was !null, i.e. it was not found
                    if(tmpCurrent != null)
                    // Remove it from currentAcc ArrayList
                        currentAcc.remove(tmpCurrent);
                }


        // Serialization and Deserialization Section...

        // A write record to file method
        // Serializes the ArrayList and reads it out into the file 

        public void WriteRecordsToFile(Current c)
        {
            final String FILENAME = "current.bin";
            try
            {
                // Serializes the ArrayList
                FileOutputStream fileStream = new FileOutputStream(FILENAME);

                ObjectOutputStream os = new ObjectOutputStream(fileStream);

                System.out.println("Writing to file.... " + c);
                os.writeObject(c);
                os.close();
            }
            catch(FileNotFoundException fNFE)
            {
                System.out.println("Cannot create file to store currentAcc.");
            }
            catch(Exception e)
            {
                System.out.println(e.getMessage());
            }
        }

        // A read record from file method
        // Deserializes the ArrayList and reads it back into program
        public void ReadRecordsFromFile()
        {
            final String FILENAME = "current.bin";

            try
            {
                FileInputStream fis = new FileInputStream(FILENAME);

                ObjectInputStream is = new ObjectInputStream(fis);

                System.out.println("Reading from file...");
                Current c;
                c = (Current)is.readObject();
                System.out.println(c);
                is.close();     
            }catch(FileNotFoundException fNFE)
            {
                System.out.println("Cannot find current file.");
            }
            catch(Exception e)
            {
                System.out.println(e.getMessage());
            }
        }   

}// end class