Serialize an object to a fileTag(s): IO


Suppose we have a class called Queue.class. We want to save the state of the Queue in a file. Since our Queue extends the Vector class, the methods needed to serialize the object are already done. All we need is an input or output stream.

First the Queue class

 import java.util.Vector;
 import java.io.*;

 public class Queue extends Vector {
  /*
  ** FIFO, first in first out
  */
  Queue() {
  super();
  }
 
 void put(Object o) {
  addElement(o);
  }

 Object get() {
  if (isEmpty()) return null;
    Object o = firstElement();
    removeElement(o);
    return o;
  }

 Object peek() {
  if (isEmpty()) return null;
    return firstElement();
    }
}
To serialize (save the Queue state to a file) :
 public static void main(String args[]) {
  Queue theQueue;
  
  theQueue = new Queue();
  theQueue.put("element 1");
  theQueue.put("element 2");
  theQueue.put("element 3");
  theQueue.put("element 4");
  System.out.println(theQueue.toString());
  
  // serialize the Queue
  System.out.println("serializing theQueue");
  try {
      FileOutputStream fout = new FileOutputStream("thequeue.dat");
      ObjectOutputStream oos = new ObjectOutputStream(fout);
      oos.writeObject(theQueue);
      oos.close();
      }
   catch (Exception e) { e.printStackTrace(); }
}
To unserialize (to load a previously saved Queue) :
  public static void main(String args[]) {
   Queue theQueue;
    
   theQueue = new Queue();
    
   // unserialize the Queue
   System.out.println("unserializing theQueue");
   try {
    FileInputStream fin = new FileInputStream("thequeue.dat");
    ObjectInputStream ois = new ObjectInputStream(fin);
    theQueue = (Queue) ois.readObject();
    ois.close();
    }
   catch (Exception e) { e.printStackTrace(); }
     
   System.out.println(theQueue.toString());     
}

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