将对象写入文件

Question

我想做的是将 HashMap 写入文件。运行时下面的代码正确。但是，当我尝试运行只将对象写入文件并尝试运行单独读取写入的对象到文件时，它会抛出以下异常。

import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.util.ArrayList;
import java.util.HashMap;

public class FileIo {
    String fileName;
    FileOutputStream fos;
    FileInputStream fis;
    ObjectOutputStream oos;
    ObjectInputStream ois;

    public FileIo(String fileName) {
        this.fileName = fileName;
        File file = new File(fileName);
        try {
            if (!file.exists()) {
                file.createNewFile();
                System.out.println("created");
            }
            fos = new FileOutputStream(fileName);
            fis = new FileInputStream(fileName);
            oos = new ObjectOutputStream(fos);
            ois = new ObjectInputStream(fis);
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    public void writeToFile(Object obj) {
        try {
            oos.writeObject(obj);
            oos.flush();
            oos.close();
        } catch (IOException e) {
            e.printStackTrace();

        }

    }

    public Object readFromFile() {
        try {
            return ois.readObject();
        } catch (ClassNotFoundException | IOException e) {
            e.printStackTrace();
        }

        return null;

    }

    @SuppressWarnings("unchecked")
    public static void main(String args[]) {
        HashMap<String, ArrayList<String>> map = new HashMap<String, ArrayList<String>>();
        FileIo fi = new FileIo("tex.txt");
        //Only write to the file
        ArrayList<String> a = new ArrayList<>();
        a.add("test");
        map.put("testput", a);
        fi.writeToFile(map);
        //Only write to the file
        try {
            Thread.sleep(5000);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        //Only read from the file
        map = null;
        map = (HashMap<String, ArrayList<String>>) fi.readFromFile();
        System.out.println(map.toString());
    }
}

//异常

    java.io.EOFException
    at java.io.ObjectInputStream$BlockDataInputStream.peekByte(ObjectInputStream.java:2608)
    at java.io.ObjectInputStream.readObject0(ObjectInputStream.java:1319)
    at java.io.ObjectInputStream.readObject(ObjectInputStream.java:371)
    at FileIo.readFromFile(FileIo.java:49)
    at FileIo.main(FileIo.java:73)

唯一不同的是不是直接写入并立即读取它。我先写对象程序完成然后运行程序运行s 读取对象。

Answer 1

您需要在数据写入文件后创建 FileInputStream。

您不能在之前创建它并假定它会显示随后写入的数据。

将对象写入文件

Writing an object to the file

java

eofexception