Develop an application that has to deal with Library Holdings, including Books, Magazines, and Multimedia Resources (This might be a program used by the Librarian to add newly acquired Library Holdings). The program could use a class name Library to represent all types of library resources.
The Library Class would include data members such as ID, Date of Acquisition, Description, number of copies, title andinstance methods such addItem() and retrieveItem() also accessor and mutator methods are needed to accecss data members. These are variables and method common to all Library Holdings. The three subclasses of Library - Books, Magazines, and Multimedia - could then use to hold data members and methods specific to particular Library Holdings. The Books class member contains author, publisher and ISBN as its data members and accessor and mutator methods. The Magazines class member includes magazine edition and date issued as its data members, accessor and mutator for its methods. Lastly the class Multimedia may contain the subject and type for its data members together with a accessor and mutator. Use arrays to store Library Holdings. Provide an interface using swing components for your application.
above is the problem. i can't understand the bold parts in the problem, and here is currently where im at. could someone please put me on the right track here? 

/**
 * @(#)Library.java
 *
 *
 * @author 
 * @version 1.00 2013/1/12
 */
 
 
public class Library 
{
	int id;
	String date;
	String description;
	int copies;
	String title;
	Library item;
 
	public void addItem()
	{
 
	}
 
	public Library retrieveItem()
	{
 
	}
 
	public void setId(int temp)
	{
		id = temp;
	}
 
    public int getID()
    {
    	return id;
    }
 
    public void setDate(String temp)
    {
    	date = temp;
    }
 
    public String getDate()
    {
    	return date;
    }
 
    public void setDescription(String temp)
    {
    	description = temp;
    }
 
    public String getDescription()
    {
    	return description;
    }
 
    public void setCopies(int temp)
    {
    	copies = temp;
    }
 
    public int getCopies()
    {
    	return copies;
    }
 
    public void setTitle(String temp)
    {
    	title = temp;
    }
 
    public String getTitle()
    {
    	return title;
    }
 
 
}