the code

public class Printer {

String status = “Idle”;

Vector jobs;

public boolean print (User u, Book b) {

PostScript ps=get_ps(b);

Job newJob = new Job (ps, u.get_name());

return queue(newJob);

}

boolean queue(Job j) {

//...

return true;

}

}

Book

Printer

User

Library

class Library {

Hashtable books;

Library(){

books = new Hashtable(100);

}

public Book getBook(User u, String title) {

System.out.println("REQUEST TO GET BOOK " + title);

if(books.containsKey(title)) {

Book b = (Book)books.get(title);

System.out.println("getBook: Found it:" + b);

if (b != null) {

if (b.get_borrower() == null) {

b.set_borrower(u);

return b;

}

}

}

return null;

}

}

class User {

private String name;

Library theLibrary;

Printer thePrinter;

public User(String n) { name = n; }

public boolean getBook (String title) {

Book aBook = theLibrary.getBook(this, title);

thePrinter.print(this,aBook);

return true;

}

}

class Book {

private String title;

private String author;

private String isbn;

private PostScript ps;

private User borrower;

public Book(String t, String a, String i, PostScript p) {

title = t;

author = a;

isbn = i;

ps = p;

}

public User get_borrower() {return borrower;}

public void set_borrower(User u) {borrower = u;}

public PostScript get_ps() { return ps; }

}

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