Input and output Streams in java

Question

I know that this question may be answered, but I can't find a solution. I have a book class and I create objects. What I want is that each time I create an object, it is saved to a file books.txt. I also need to be able to open this file and read it at any time and be able to search an object by its parameters ex::(String name) . I have read a lot of topics but I can't find a solution.

When I try to open my file and search for the objects, the first object is being printed fine, but when it opens the second object it gives me errors like:

java.io.StreamCorruptedException: invalid type code: AC
    at java.io.ObjectInputStream.readObject0(ObjectInputStream.java:1379)
    at java.io.ObjectInputStream.readObject(ObjectInputStream.java:371)
    at Search.deserialzeBookName(Search.java:80)
    at Search$1.actionPerformed(Search.java:58)   

Code:

 public void saveAll() {
  int day = Integer.parseInt(arrDay.getText());
  int month = Integer.parseInt(arrMonth.getText());
  int year = Integer.parseInt(arrYear.getText());
  this.date1 = new GregorianCalendar(year, month, day).getTime();

  day = Integer.parseInt(deppDay.getText());
  month = Integer.parseInt(deppMonth.getText());
  year = Integer.parseInt(deppYear.getText());
  this.date2 = new GregorianCalendar(year, month, day).getTime();

  //System.out.println(date1);v
  Book b;
  b = new Book(onoma.getText(), epitheto.getText(), tilefono.getText(), date1, date2, toType(domatio.getText()), check());//dates
  File f = new File ("books.txt");

  try {
    FileOutputStream fout = new FileOutputStream("books.txt",true);
    ObjectOutputStream oos = new ObjectOutputStream(fout);
    oos.writeObject(b);
    oos.close();
    System.out.println("Done");

  } catch (FileNotFoundException e) {
    System.err.println("FileNotFound error");
    e.printStackTrace();
  } catch (IOException e) {
    System.err.println("IOException error");
    e.printStackTrace();
  }
}

Search function:

public Book deserialzeBookName(){
  Book address;
  try{
    FileInputStream fin = new FileInputStream("books.txt");
    ObjectInputStream ois = new ObjectInputStream(fin);
    while((address =(Book) ois.readObject()) !=null){
      System.out.println(address);
    }

    ois.close();
    //address = (Book) ois.readObject();
    //ois.close();

    return address;
  }catch(Exception ex){
    ex.printStackTrace();
    return null;
  } 
}