Java.io.ObjectInputStream.readFields() Method



Description

The java.io.ObjectInputStream.readFields() method reads the persistent fields from the stream and makes them available by name.

Declaration

Following is the declaration for java.io.ObjectInputStream.readFields() method.

public ObjectInputStream.GetField readFields()

Parameters

NA

Return Value

google.gr

This method returns the GetField object representing the persistent fields of the object being deserialized.

Exception

  • ClassNotFoundException − If the class of a serialized object could not be found.

  • IOException − If an I/O error has occurred.

  • NotActiveException − If the stream is not currently reading objects.

Example

The following example shows the usage of java.io.ObjectInputStream.readFields() method.

package com.tutorialspoint;

import java.io.*;

public class ObjectInputStreamDemo {
   public static void main(String[] args) {
      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(new Example());
         oout.flush();

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

         // read the object and print the string
         Example a = (Example) ois.readObject();

         // print the string that is in Example class
         System.out.println("" + a.s);

      } catch (Exception ex) {
         ex.printStackTrace();
      }
   }

   static class Example implements Serializable {
      String s = "Hello World!";

      private String readObject(ObjectInputStream in) 
         throws IOException, ClassNotFoundException {

         // call readFields in readObject
         ObjectInputStream.GetField gf = in.readFields();

         // save the string and return it
         return (String) gf.get("s", null);
      }
   }
}

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

Hello World!
java_io_objectinputstream.htm
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