Java.io.ObjectOutputStream.writeObject() Method

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Description

The java.io.ObjectOutputStream.writeObject(Object obj) method writes the specified object to the ObjectOutputStream. The class of the object, the signature of the class, and the values of the non-transient and non-static fields of the class and all of its supertypes are written. Default serialization for a class can be overridden using the writeObject and the readObject methods. Objects referenced by this object are written transitively so that a complete equivalent graph of objects can be reconstructed by an ObjectInputStream.

Declaration

Following is the declaration for java.io.ObjectOutputStream.writeObject() method.

public final void writeObject(Object obj)

Parameters

obj − The object to be written.

Return Value

This method does not return a value.

Exception

• InvalidClassException − Something is wrong with a class used by serialization.

• NotSerializableException − Some object to be serialized does not implement the java.io.Serializable interface.

• IOException − Any exception thrown by the underlying OutputStream.

Example

The following example shows the usage of java.io.ObjectOutputStream.writeObject() method.

package com.tutorialspoint;

import java.io.*;

public class ObjectOutputStreamDemo {
   public static void main(String[] args) {
      String s = "Hello world!";
      int i = 897648764;
      
      try {
         // create a new file with an ObjectOutputStream
         FileOutputStream out = new FileOutputStream("test.txt");
         ObjectOutputStream oout = new ObjectOutputStream(out);

         // write something in the file
         oout.writeObject(s);
         oout.writeObject(i);

         // close the stream
         oout.close();

         // create an ObjectInputStream for the file we created before
         ObjectInputStream ois = new ObjectInputStream(new FileInputStream("test.txt"));

         // read and print what we wrote before
         System.out.println("" + (String) ois.readObject());
         System.out.println("" + ois.readObject());
      } catch (Exception ex) {
         ex.printStackTrace();
      }
   }
}

Let us compile and run the above program, this will produce the following result −

Hello world!
897648764