java - 文件的奇怪输出

Question

我在读取文件时获得的输入有问题。

该文件是在另一个 Activity 中制作的，非常简单:

ArrayList stuff = new ArrayList();
stuff.add("1,2,3");

try{
String saveFile = "saveGamesTest1.csv";
FileOutputStream saveGames = openFileOutput(saveFile, getApplicationContext().MODE_APPEND);    

ObjectOutputStream save = new ObjectOutputStream(saveGames);

save.writeObject(stuff);    
save.close(); }

在其他 Activity 中，它正在通过

读取

try {
            FileInputStream fileIn=openFileInput("saveGamesTest1.csv");
            InputStreamReader InputRead = new InputStreamReader(fileIn);

            Scanner s = new Scanner(InputRead).useDelimiter(",");
            System.out.println(s.next());
            System.out.println(s.next());
            System.out.println(s.next());

        }

我期待(并希望)得到像这样的结果

1
2
3

但是，我得到的结果是这样的:

/storage/emulated/0/Android/data/ys.test/files/saveGamesTest1.csv����sr��java.util.ArrayListx����a���I��sizexp������w������t��1
2
3x

我做错了什么？
。

编辑
我按照下面的建议尝试了序列化，如下所示:

public class Save implements java.io.Serializable {
        public String name;
        public String address;
        public transient int SSN;
        public int number;

    }


    public void save(){

        Save e = new Save();
        e.name = "Reyan Ali";
        e.address = "Phokka Kuan, Ambehta Peer";
        e.SSN = 11122333;
        e.number = 101;

        try {
            String saveFile = "save.ser";
            FileOutputStream saveGames = openFileOutput(saveFile, getApplicationContext().MODE_APPEND);
            ObjectOutputStream out = new ObjectOutputStream(saveGames);
            out.writeObject(e);
            out.close();
            saveGames.close();
            System.out.printf("Serialized data is saved in save.csv");
        }
        catch(IOException i) {
            i.printStackTrace();
            out.println("Save exception gepakt");
        }
    }  

但是，out.writeObject(e); 给出错误，指出这不是可序列化的

Answer 1

您没有将对象存储为 csv，而是将其存储为序列化 java 对象，您必须将其作为对象而不是 csv 文件读取

看这里https://www.tutorialspoint.com/java/java_serialization.htm在序列化对象部分

你必须使用

FileInputStream in = null;
ObjectInputStream ois = null;
ArrayList stuff2 = null;
try {
    in = openFileInput("saveGamesTest1.csv");
    ois = new ObjectInputStream(in);
    stuff2 = (ArrayList) ois.readObject();
} catch(IOException e) {...}
catch(ClassNotFoundException c) {...}
finally {
    if (ois != null) {
        ois.close();
    }
    if (in != null) {
        in.close();
    }
}

如果您想要一个 csv 文件，您必须通过迭代数组并在文件中一一写入值并添加分隔符来构建它，或者按照此操作 How to serialize object to CSV file?

编辑:Java 7 中序列化对象(这里是与您的示例类似的列表)和反序列化的优雅方式:

public class Main {

public static void main(String[] args) {
    List<Integer> lists = new ArrayList<>();
    List<Integer> readList = null;
    String filename = "save.dat";
    lists.add(1);
    lists.add(2);
    lists.add(3);

    //serialize
    try (ObjectOutputStream oos = new ObjectOutputStream(new FileOutputStream(filename))) {
        oos.writeObject(lists);
    } catch (IOException e) {
        e.printStackTrace();
    }
    //don't need to close because ObjectOutputStream implement AutoCloseable interface

    //deserialize
    try (ObjectInputStream oos = new ObjectInputStream(new FileInputStream(filename))) {
        readList = (List<Integer>) oos.readObject();
    } catch (IOException | ClassNotFoundException e) {
        e.printStackTrace();
    }
    //don't need to close because ObjectInputStream implement AutoCloseable interface


    //test
    if(!lists.equals(readList)) {
        System.err.println("error list saved is not the same as the one read");
    }
}

}