readingmaterial.java

JavaTM 2 SDK, Standard Edition Documentation

/*
 * Copyright 2002 Sun Microsystems, Inc. All  Rights Reserved.
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 * Redistribution and use in source and binary forms, with or 
 * without modification, are permitted provided that the following 
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 *  notice, this list of conditions and the following disclaimer.
 * 
 * -Redistribution in binary form must reproduce the above copyright 
 *  notice, this list of conditions and the following disclaimer in 
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 *  distribution.
 *  
 * Neither the name of Sun Microsystems, Inc. or the names of 
 * contributors may be used to endorse or promote products derived 
 * from this software without specific prior written permission.
 * 
 * This software is provided "AS IS," without a warranty of any 
 * kind. ALL EXPRESS OR IMPLIED CONDITIONS, REPRESENTATIONS AND 
 * WARRANTIES, INCLUDING ANY IMPLIED WARRANTY OF MERCHANTABILITY, 
 * FITNESS FOR A PARTICULAR PURPOSE OR NON-INFRINGEMENT, ARE HEREBY 
 * EXCLUDED. SUN AND ITS LICENSORS SHALL NOT BE LIABLE FOR ANY 
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 *  
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 */

import java.io.*;

/** 
 * The Externalizable Superclass:
 *  When the Externalizable Subclass Book implements its writeExternal and
 *  readExternal Methods, it needs to save the state of its superclass using 
 * the superclass's writeExternal and readExternal Methods
 */
public class ReadingMaterial implements Externalizable {

    /* 
     * In order for us to be able to serialize this data, these must be
     * either serializable/externalizable objects or primitive data types. 
     */
    private  String author;
    private  String subject;
    private  int yearwritten;

    // other relevant data and methods 
    // .
    // .
    // .
  
    /* 
     * Must have a public no-arg constructor when implementing Externalizable
     */
    public ReadingMaterial() {}
    
    /** 
     * Initialize the fields
     *
     */
    public ReadingMaterial(String auth, String sub, int year) {
	author = auth;
	subject = sub;
	yearwritten = year;
    }
    
    /**
     * A public field access method, since the data fields are private and 
     * will need to be accessed by the subclass to print them or use them 
     * otherwise.
     */
    public String getAuthor() { 
	return author; }
    /**
     * A field access method, since the data fields are private and will need
     * to be accessed by the subclass to print them or use them otherwise.
     */
    public String getSubject() { 
	return subject; }
    /**
     * A field access method, since the data fields are private and will need
     * to be accessed by the subclass to print them or use them otherwise.
     */
    public int getYearwritten() { 
	return yearwritten; }

    /**
     * Mandatory writeExternal method. 
     * @serialData Write author and subject field as objects and then write
     *             yearwritten field as an integer.
     */
    public void writeExternal(ObjectOutput out) throws IOException {
    
	out.writeObject(author);
	out.writeObject(subject);
	out.writeInt(yearwritten);
  }

    /**
     * Mandatory readExternal method. Will read in the data that we wrote out
     * in the writeExternal method. MUST BE IN THE SAME ORDER and type as we
     * wrote it out. By the time, readExternal is called, an object of this 
     * class has already been created using the public no-arg constructor,
     * so this method is used to restore the data to all of the fields of the 
     * newly created object.
     */
  public void readExternal(ObjectInput in) throws IOException, ClassNotFoundException {
   
    author = (String)in.readObject();
    subject = (String)in.readObject();
    yearwritten = in.readInt();
  }
}