如何使用Java中的ObjectInputStream读取不同的Object

Question

Note: it's not a duplicate, because here we want to write not only Objects, but also a whole file, then read it back.

I have created a single File with 3 Objects using ObjectOutputStream ,

1. String
2. String
3. File ( size is between [1 to 1.5]GB )

Below is my code whichever I have used to write the File

byte[] BUFFER = new byte[1024*32];
FileInputStream fis = new FileInputStream("ThisIsTheFile.xyz");
FileOutputStream fos = new FileOutputStream("abcd.dat", true);
ObjectOutputStream oos = new ObjectOutputStream(fos);      

String fileId = "BSN-1516-5287B-65893", fTitle = "Emberson Booklet";      

for(int i = 0; i < 3; i++){      
    if(i == 0){      
        oos.write(fileId.getBytes(), 0, fileId.length());
    }else if (i == 1){
        oos.write(fTitle.getBytes(), 0, fTitle.length());
    }else{
        InputStream is = new BufferedInputStream(fis);
        int bytesRead = -1;
        while((bytesRead = is.read(BUFFER)) != -1){
            oos.write(BUFFER, 0, bytesRead);
        }
        is.close();
    }
}

fileId = fTitle = null;

oos.flush();
oos.close();
fos.flush();
fos.close();
fis.close();

Now my problem is:

1. I don't want to interrupt the Java Heap Space so read & write the large File streams using 32KB bytes buffer technique simultaneously.
2. Am I writing these three Object inside a single File separately & correctly?
3. Last but not least, How should I retrieve these above said all 3 Object through ObjectInputStream from "abcd.dat" File ?

Please help.

Answer 1

I have create a file with 3 single objects

No. You have created a file with no objects and a whole lot of bytes, and no way of telling where one byte sequence stops and another starts. Use writeObject(), and read them with readObject() . The way you have it, there's no point in using ObjectOutputStream at all.

Note: appending to this file won't work. See here for why.