为什么我不能正确地从文件中获取对象?

我有一个自定义对象列表,我先编写然后读取到文件中。

这是我的课:

public class Book implements Serializable{
   private int isbn;
   private String category;
   private String authorName;

    public int getIsbn() {
        return isbn;
    }

    public String getCatId() {
        return category;
    }


    public void setIsbn(int isbn) {
        this.isbn = isbn;
    }

    public void setCategory(String category) {
        this.category = category;
    }


    public void setAuthorName(String authorName) {
        this.authorName = authorName;
    }

    public String getAuthorName() {
        return authorName;
    }

    public Book() {}

    //copy book 
    public Book(Book book, int id) {
        this.category = book.category;
        this.title = book.title;
        this.authorName = book.authorName;
        this.isbn = id;
    } 
}

下面是我用来编写对象列表的函数:

private static <T> void writeToFile(List<T> items, String fileName) {
    try {
        String path = "src\\hw1\\library\\repos\\" + fileName;

        FileOutputStream f = new FileOutputStream(path, true);// true- means append to file
        ObjectOutputStream o = new ObjectOutputStream(f);

        // Write objects to file
        o.writeObject(items);
        o.close();
        f.close();
    } catch (Exception e) {}
}

下面是我从列表中读到的函数:

private static <T> List<T> readFromFile(Context context, String fileName) {
    try {
         String path = "src\\hw1\\library\\repos\\" +fileName ;

         FileInputStream fi = new FileInputStream(path);
         ObjectInputStream oi = new ObjectInputStream(fi);
         // Read objects
         List<T> items = (List<T>)oi.readObject();
         oi.close();
         fi.close();

         return items;
    } catch (Exception e) {}
    return null;
}

对象列表被写入文件,

知道为什么我从第一次写入文件的仅文件对象中获取吗?