加载和保存 LinkedLists from/to 文件

Question

我正在研究库存控制程序。我有一个用于每个可用项目的 StockItem 对象，以及一个用于存储多个不同 StockItem 对象的 StockLinkedList。我想知道是否有办法将我当前的 LinkedList 保存到文件，并使用对象流再次加载它。我试图尝试使用 FileOutputStream 和 ObjectOutputStream 但无济于事。任何帮助将不胜感激。

目前我的 StockLinkedList class 的准系统如下：

import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.ObjectOutputStream;
import java.util.*;

public class StockLinkedList implements StockList {

    LinkedList<StockItem> stockItemList;

    public StockLinkedList(){
        stockItemList = new LinkedList<>();
    }

    public void loadStockData(String filename){
        try {
            FileOutputStream stockFile = new FileOutputStream(filename + ".dat");
        } catch (FileNotFoundException e) {
            System.out.println("File not found!");
        }
    }

    public void saveStockData(){
        ObjectOutputStream save = ObjectOutputStream(saveFile);
        save.writeObject(objectToSave);
        save.close();
    }

}

Answer 1

我建议您使用 Json 序列化。使用 Gson 库的启动示例。

    public static List<Weight> importDataFromFile(String path) {
        Gson g = new Gson();
        String s = FileHelper.readTextFromFile(path); (just read text from file)
        Type listType = new TypeToken<ArrayList<Weight>>() {
        }.getType();
        return g.fromJson(s, listType);
    }

    public static int exportDataToFile(String path, List<Weight> weights) {
       Gson g = new Gson();
       FileHelper.writeTextToFile(path, g.toJson(weights));
    }

我的示例中的权重对象是简单的 POJO。例如：

public class Weight {
    private long date;
    private int value;
    private String unit;
    //geters setters
}

Answer 2

如果您只想将对象的状态保存在文件中（序列化为文件），我建议您实现以下方法：

/**
 * This method will write your stock information into a file
 * @param path Is the target path in your file system
 * @param list Is the list you want to save
 * @throws IOException 
 * @throws FileNotFoundException 
 */
public void writeStockInfo(String path, LinkedList<StockItem> list) throws FileNotFoundException, IOException {
    //1. Point to your file using File
    File file =  new File(path);
    //2. Then use OOS but to serialize into a file you should use FileOutputStream inside the invocation
    ObjectOutputStream objectOutputStream = new ObjectOutputStream(new FileOutputStream(file));
    //3. Just write the object to a file using the method "writeObject"
    objectOutputStream.writeObject(list);
    //4. Close the streams
    objectOutputStream.close();
}

/**
 * This method will read the information of the stock in a file
 * @param path Is the file from which you will read the info
 * @return
 * @throws IOException 
 * @throws FileNotFoundException 
 * @throws ClassNotFoundException 
 */
public LinkedList<StockItem> readStockInfo(String path) throws FileNotFoundException, IOException, ClassNotFoundException {
    LinkedList<StockItem> infoList = new LinkedList<StockItem>();
    //1. Point to your file (the one you want to read)
    File fileToRead = new File(path);
    //2. Use OIS to read the information from a file using FileInputStream
    ObjectInputStream objectInputStream = new ObjectInputStream(new FileInputStream(fileToRead));
    //3. Just read the object and cast to make sure you obtain the right object
    infoList = (LinkedList<StockItem>) objectInputStream.readObject();
    //4. Close the stream
    objectInputStream.close();
    return infoList;
}

只需确保您的 "StockItem" class 正在实现 Serializable 接口。

顺便说一句：我编辑它是因为我忘记关闭流了（真丢人！）

希望对您有所帮助。

编码愉快:)

加载和保存 LinkedLists from/to 文件

Loading and Saving LinkedLists from/to file

java

linked-list

object