java 从文件中读取 ArrayList 作为对象？
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Reading ArrayList as object from file?
提问by Dniel Woody
Alright, so I have done the following:
好的，所以我做了以下事情：
I've added objects to an ArrayList and written the whole list as an object to a file.
The problem is when trying to read them back as a whole. I get the following error:
我已将对象添加到 ArrayList 并将整个列表作为对象写入文件。
问题是当试图将它们作为一个整体读回时。我收到以下错误：
Exception in thread "main" java.lang.ClassCastException: java.util.Arrays$ArrayList cannot be cast to java.util.ArrayList at persoana.Persoana.main(Student.java:64)
线程“main”中的异常 java.lang.ClassCastException：java.util.Arrays$ArrayList 无法转换为 persoana.Persoana.main(Student.java:64) 处的 java.util.ArrayList
Here's my code: (Everything is in a try catch so nothing to worry about that)
这是我的代码：（一切都在 try catch 中，所以不用担心）
Writing
写作
Student st1 = new Student("gigi","prenume","baiat","cti");
Student st2= new Student("borcan","numegfhfh","baiat cu ceva","22c21");
List <Student> studenti = new ArrayList<Student>();
studenti = Arrays.asList(st1,st2);
FileOutputStream fos = new FileOutputStream("t.ser");
ObjectOutputStream oos = new ObjectOutputStream(fos);
oos.writeObject(studenti);
oos.close();
Reading
阅读
FileInputStream fis = new FileInputStream("t.ser");
ObjectInputStream ois = new ObjectInputStream(fis);
ArrayList <Student> ds;
ds = (ArrayList <Student>)ois.readObject();
ois.close();
The problem occurs at this line:
问题发生在这一行：
ds = (ArrayList <Student>)ois.readObject();
回答by Hyman
I guess that the problem is that you are creating the Listof Studentthrough Arrays.asList. This method doesn't return an ArrayListbut an Arrays.ArrayListwhich is a different class, meant to backen an Array and to be able to use it as a List. Both ArrayListand Arrays.ArrayListimplement Listinterface but they are not the same class.
我想问题在于您正在创建Listof Studentthrough Arrays.asList。此方法不返回 anArrayList而是Arrays.ArrayList一个不同的类，旨在支持 Array 并能够将其用作List. 双方ArrayList并Arrays.ArrayList实现List接口，但它们不是同一类。
You should cast it to appropriate object:
您应该将其转换为适当的对象：
List<Student> ds = (List<Student>)ois.readObject();
回答by munyengm
Change the following lines:
更改以下几行：
ArrayList <Student> ds;
ds = (ArrayList<Student>)ois.readObject();
to
到
List<Student> ds = (List<Student>)ois.readObject();
