Java读取/写入多个对象到文件

Question

我正在尝试学习如何使用 Steam，但我似乎无法理解。我想要做的是将几个单独的对象添加到一个文件中，然后一次检索它们。当我尝试检索它们时，我只得到“最后”插入的对象。现在我正在尝试弄清楚如何打印对象，但后来我想将它们导入到 ArrayList 中。这是我的代码:

public class ExpenseDB {
private final static File DB = new File("C:\\Expense2s3.dat");

public static void addExpense(Expense ex) throws AddException {
        try {
            ObjectOutputStream out;
            out = new ObjectOutputStream(new FileOutputStream(DB));
            out.writeObject(ex);
            out.close();
            System.out.println("Added "+ex);
        } catch (IOException e) {
            throw new AddException();
        }
}


@SuppressWarnings("deprecation")
public static void getAllExpenses() {
    if (DB.length() == 0) return;
    try {
        ObjectInputStream in = new ObjectInputStream(new FileInputStream(DB));
        try {
            Expense exp=(Expense)in.readObject();
            System.out.println(exp);
            in.close();
         } catch (ClassNotFoundException e) {}
    } catch (IOException e) {
        System.err.println("Error");
    }
}

Answer 1

当你打开一个文件然后写入它时，它会覆盖它的内容。而是使用 new FileOutputStream(DB,true)追加到文件末尾