java-从二进制文件中读取arraylist集合，并在新数组中分配每个元素

Question

Previously, I have wrote a arraylist data into a binary file called (ItStateBinary.dat)

and now I am trying to read the arraylist from the binary file, then assign each of the element in arraylist to the array.

so far i have this:

public CarOwner[] readListFromBinary() throws Exception
{
    String fileName = "ItStateBinary.dat";
    FileInputStream inStream = new FileInputStream(fileName);
    ObjectInputStream objectInputFile = new ObjectInputStream(inStream);

    //need to create CarOwner[] object called temp and return
}

readListFromBinary() method Reads an ArrayList collection from a binary file (ltStateBinary.dat). Then, each ArrayList object item is then written to a newly created CarOwner[] called temp. temp is returned to the calling method.

edit:

 public CarOwner[] readListFromBinary() throws Exception
{
    String fileName = "ItStateBinary.dat";
    FileInputStream inStream = new FileInputStream(fileName);
    ObjectInputStream objectInputFile = new ObjectInputStream(inStream);

    ArrayList<CarOwner> read = (ArrayList<CarOwner>)objectInputFile.readObject();

    CarOwner[] temp = read.toArray(new CarOwner[read.size()]); 
    return temp;
}

does anybody know whats wrong with this method? it gives me compiler warning

Answer 1

I'm not sure what you asking, but assuming that you write your ArrayList to the file like that:

ArrayList<CarOwner> al = new ArrayList<CarOwner>();
FileOutputStream fos = new FileOutputStream("ItStateBinary.dat");
ObjectOutputStream oos = new ObjectOutputStream(fos);
oos.writeObject(al);

That way, you can just read the way, your are already doing:

FileInputStream fis = new FileInputStream("ItStateBinary.dat");
ObjectInputStream ois = new ObjectInputStream(fis);
ArrayList<CarOwner> read = (ArrayList<CarOwner>)ois.readObject();

Then just return you return the array from your ArrayList:

return read.toArray(new CarOwner[read.size()]);