Question

可能重复：
How to Serialize an ArrayLIst in java without getting errors?

我在两个不同的班级中有两个arraylists。一种是存储交易对象temporarily＆amp;其他permanent。我使用addAll方法将对象从temporary arraylist复制到permanent。然后将对象从permanent arraylist保存到file。当我的程序重新启动时，permanent arraylists中的对象将从file恢复。但我得到一个例外。我的代码怎么了？

import java.io.FileInputStream; import java.io.FileOutputStream; import java.io.ObjectInputStream; import java.io.ObjectOutputStream; import java.util.ArrayList;

/ ** * * @author Haleemdeen * / public class FileImportExport {

private ArrayList<Stock> permntTransactions=new ArrayList<Stock>();


void cancatToPerrmntTransactions(ArrayList<Stock> arraylist1){
    permntTransactions.addAll(arraylist1);
}

ArrayList<Stock> displayPermntTransactions(){
    return permntTransactions;
}

    void exportToFile(){

    try{  // Catch errors in I/O if necessary.
    // Open a file to write to, named SavedObj.sav.
    FileOutputStream saveFile=new FileOutputStream("SaveObj.sav");

    // Create an ObjectOutputStream to put objects into save file.
    ObjectOutputStream save = new ObjectOutputStream(saveFile);

    // Now we do the save.
    save.writeObject(permntTransactions);

    // Close the file.
    save.close(); // This also closes saveFile.
    }
    catch(Exception exc){
    exc.printStackTrace(); // If there was an error, print the info.
    }
}

        void importFromFile(){

    try{
    // Open file to read from, named SavedObj.sav.
    FileInputStream saveFile = new FileInputStream("SaveObj.sav");

    // Create an ObjectInputStream to get objects from save file.
    ObjectInputStream save = new ObjectInputStream(saveFile);

    // Now we do the restore.
    // readObject() returns a generic Object, we cast those back
    // into their original class type.

    permntTransactions = (ArrayList<Stock>) save.readObject();

    // Close the file.
    save.close(); // This also closes saveFile.
    }
    catch(Exception exc){
    exc.printStackTrace(); // If there was an error, print the info.
    }

    // Print the values, to see that they've been recovered.
    System.out.println("\t\t" + permntTransactions);
    System.out.println();
} }

主要方法：

FileImportExport file1=new FileImportExport();
file1.cancatToPerrmntTransactions(transactions);
file1.exportToFile();

这是我得到的例外：

java.io.NotSerializableException：m_media_cdstore.Stock at java.io.ObjectOutputStream.writeObject0（ObjectOutputStream.java:1156） at java.io.ObjectOutputStream.writeObject（ObjectOutputStream.java:326） at java.util.ArrayList.writeObject（ArrayList.java:570） at sun.reflect.NativeMethodAccessorImpl.invoke0（Native Method） at sun.reflect.NativeMethodAccessorImpl.invoke（NativeMethodAccessorImpl.java:39） at sun.reflect.DelegatingMethodAccessorImpl.invoke（DelegatingMethodAccessorImpl.java:25）在java.lang.reflect.Method.invoke（Method.java:597）在java.io.ObjectStreamClass.invokeWriteObject（ObjectStreamClass.java:945）

Answer 1

要序列化的类（在本例中为Stock）必须实现Serializable interface。

Answer 2

Stock类必须实现Serializable，并且其所有字段（完全深度）必须实现Serializable或者是原始的。

Answer 3

尝试序列化对象时，请确保特定类（Stock。java）必须实现java.io.Serializable，如果Stock类具有必须实现的任何其他类java.io.Serializable

如何存储和;检索文件中对象的arraylist？

3 个答案: