Java.io.ObjectInputStream.getField.defaulted() Method

Description

The java.io.ObjectInputStream.getField.defaulted(String name) method skips bytes.

Declaration

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

public abstract boolean defaulted(String name)

Parameters

• name -- the name of the field

Return Value

This method returns true, if and only if the named field is defaulted

Exception

• IOException -- if there are I/O errors while reading from the underlying InputStream

• IllegalArgumentException -- if name does not correspond to a serializable field

Example

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

package com.tutorialspoint;

import java.io.*;

public class ObjectInputStreamDemo implements Serializable {

   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();
         oout.close();

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

         // read an object from the stream and cast it to Example
         Example a = (Example) ois.readObject();

         // get if variable string is default in Example class
         System.out.println("" + a.isDefault);

         // print the string of a
         System.out.println("" + a.string);

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

   }

   static public class Example implements Serializable {

      static String string = "Hello World!";
      static boolean isDefault;
	  
      // assign a new serialPersistentFields 
      private static final ObjectStreamField[] serialPersistentFields = {
         new ObjectStreamField("string", String.class)
      };

	  // create a custom readObject method
      private void readObject(ObjectInputStream in)
              throws IOException, ClassNotFoundException {

         // get the field and assign it at string variable
         ObjectInputStream.GetField fields = in.readFields();

         // check if string is defaulted, meaning if it has no value
         isDefault = fields.defaulted("string");
         string = (String) fields.get("string", null);
      }
	  
	  // create a custom writeObject method
	  private void writeObject(ObjectOutputStream out)
              throws IOException {

         // write into the ObjectStreamField array the variable string
         ObjectOutputStream.PutField fields = out.putFields();
         fields.put("string", string);
         out.writeFields();

      }
   }
}

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

false
Hello World!