无法从文件中读取对象并将它们放到java中的链接列表中

Question

我想从文件中读取对象并将数据放置到LinkedList并将引用返回给它。但是当我尝试这个方法时，它返回没有数据的LinkedList。

private static LinkedList<Course> readFromFile(String fileName) 
     throws FileNotFoundException, IOException { 
    LinkedList<Course> tmp = new LinkedList<Course>(); 

    reader = new ObjectInputStream(new FileInputStream(fileName)); 

    try { 
     LinkedList<Course> readObject2 = (LinkedList<Course>) reader 
       .readObject(); 
     LinkedList<Course> readObject = readObject2; 
     tmp = readObject; 
    } catch (ClassNotFoundException e) { 
     e.printStackTrace(); 
    } 

    return tmp; 
} 

我的写作方法看起来像这样

private static boolean writeToFile(String fileName, LinkedList<Course> templist) 
     throws IOException { 
    LinkedList<Course> templist1 = new LinkedList<Course>(); 

    if (createFile(fileName)) { 
     FileOutputStream outF = new FileOutputStream(fileName); 

     outO = new ObjectOutputStream(outF); 
     outO.writeObject(templist1); 

     //outO.flush(); 
     return true; 
    } 
    else 
     return false; 
} 

---

写作方法看起来像这样

private static boolean writeToFile(String fileName, LinkedList<Course> templist) throws IOException { 
    LinkedList<Course> templist1 = new LinkedList<Course>(); 

    if (createFile(fileName)) { 
     FileOutputStream outF = new FileOutputStream(fileName); 

     outO = new ObjectOutputStream(outF); 
     outO.writeObject(templist1); 

     //outO.flush(); 
     return true; 
    } 
    else 
     return false; 
} 

Answer 1

类实现java.io.Serializable课程？
当您使用ObjectInputStream从文件中读取对象时，它应该与您之前使用ObjectOutputStream存储它的顺序相同。和相同的对象类型。

如果您尝试阅读：

(LinkedList<Course>) reader.readObject(); 

你必须有店呢喜欢：

ObjectOutputStream writer = new ObjectOutputStream(
     new FileOutputStream(fileName)); 

writer.writeObject(yourLinkedListToSave); 

当你的代码如下：

private static boolean writeToFile(String fileName, LinkedList<Course> templist) throws IOException { 
    // Dont forget to initialize with your list else the list still empty 
    LinkedList<Course> templist1 = new LinkedList<Course>(templist); 

    if (createFile(fileName)) { 
     FileOutputStream outF = new FileOutputStream(fileName); 

     outO = new ObjectOutputStream(outF); 
     outO.writeObject(templist1); 

     //outO.flush(); 
     return true; 
    } 
    else 
     return false; 
}