Mine

//winkel.java

    private ArrayList<Cd> cdWinkel = new ArrayList<Cd>();
    private String fileName = "cd.dat";
    private Cd ingelezenCd;

    public void write(String fileName) {
       try{
           ObjectOutputStream out = new ObjectOutputStream(new FileOutputStream(fileName));
           for(Object o : cdWinkel){
                if(out.equals(o) == false){
                   out.writeObject(o);
                }

           }
           out.close();
       }
       catch(IOException i){
           i.printStackTrace();
       }
    }

    
    public void read( String fileName ) {
        try{
            ObjectInputStream in = new ObjectInputStream(new FileInputStream(fileName));
             
            while(in != null){
                ingelezenCd = (Cd) in.readObject(); 
                cdWinkel.add(ingelezenCd);
            }
            in.close();

        }
        catch(IOException i){
            i.printStackTrace();
        }
        catch(ClassNotFoundException c){
            c.printStackTrace();
        }
    }
//einde winkel.java
//gui.java
    private void performOpen() {
        String fileName = "cd.dat";
        winkel.read(fileName);
    }

    private void performSluit() {
        String fileName = "cd.dat";
        winkel.write(fileName);
        winkel.nieuw();
    }
//einde
//einde