Table of Contents. LESSON: CASE Document Library...1

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2 Table of Contents LESSON: CASE Document Library...1 Case Description...2 LABS Creating the Document Class Adding another constructor to Document class Object Oriented Programming Vector and Hashtable Classes Using Input/Output Streams Advanced: Using Threads...6 i

3 LESSON: CASE Document Library author: Just van den Broecke organization: Just Objects B.V. Slides Labs 1. Case Description 1. Creating the Document Class 2. Adding another constructor to Document class 3. Object Oriented Programming 4. Vector and Hashtable Classes 5. Using Input/Output Streams 6. Advanced: Using Threads Resources 1

4 Case Description Creating a simple library application to store different types of documents. Find all details in labs.html here or under the 'exercises/case library' dir. CASE Document Library 1 LABS 1. Creating the Document Class Write a class Document with the following characteristics attributes int id; String title; int numberofpages; Date creationdate ; A default constructor initializing the title with "NONE", the id with 1, the number of pages with 1 and the creation date with the current date. Hint: find the Date class in java.util.date. print() method displaying the Document attributes. Write a class called Main where you define the main() method to run the application. In Main.main() create a Docoument object with new and call print() on that object. Run the program by typing java Main. 2. Adding another constructor to Document class Copy the Document class from Lab 1 and extend it such that we can enter the title, id and number of pages on the command line, in order to construct a Document object with meaningful attributes. 1. Write a second constructor with three parameters, using the overloading mechanism. 2. Extend the Main.main() method to read and parse the commandline arguments. Hint: look at the class java.lang.integer to convert a String to an int for the id and number of pages. 3. According to the number of passed arguments, call the appropriate constructor. 3. Object Oriented Programming This lab exercises the following topics: Using a hierarchy of classes with inheritance Polymorphism Static class members 1. Reuse the Document class from Lab 2. Write the following specialized classes that extend the Document class: Book (publisher : String, author : String) Magazine (frequency : String{daily, weekly, monthly} ) Deed (signaturedate : Date ) 2. Give each kind of Document a print() method displaying the document features on the screen. Tip : 2

5 you may override the method tostring() and factorize print() into the Document base class. 3. Count the total number of created Document objects and display this number. Hint: make a static member int variable in Document. 4. Create a class Library with the following skeleton (find this class under the 'exercises' dir). 1: /** 2: * Library class, simple implementation with array. 3: * <p> 4: * cases/library1/lab3 6: * $Id: Library.java,v /03/14 15:42:32 justb Exp $ 8: * 9: $Author: justb $ Just van den Broecke Just Objects 10: */ 11: public class Library { 12: // TODO: declare Document array variable; 13: 14: public Library() { 15: // TODO: create array of 10 elements; 16: } 17: 18: /** Add a document to the Library. */ 19: public void add(document document) { 20: System.out.println("**************method add()"); 21: 22: // TODO: print number of documents and add document to arraydoc; 23: 24: System.out.println("**************end method add()"); 25: } 26: 27: /** displays contents. */ 28: public void displaycontents() { 29: // TODO: print contents of arraydoc; 30: } 31: } 5. Create a Main class such that you can do the following: 1: import java.util.date; 2: 3: /** 4: * Main program. 6: * cases/library1/lab3 8: * $Id: Main.java,v /03/14 15:42:32 justb Exp $ 9: * <p> 10: * 11: $Author: justb $ Just van den Broecke Just Objects 12: */ 13: public class Main { 14: 15: public static void main(string args[]) { 16: 17: Library lib=new Library(); 18: 19: lib.add(new Book(10, "Hacking Java", 1500, "Mark Wutka", "QUE")); 20: lib.add(new Book(20, "Java 1.1 Unleashed", 1500, "Michael Morrison", "SAMS NET")); 21: lib.add(new Magazine(30, "Java Report", 60, "monthly", "SIGS")); 22: lib.add(new Deed(40, "Booker prize", 60, new Date(99, 5, 12))); 23: 24: lib.displaycontents(); 25: } 26: } 27: 3

6 4. Vector and Hashtable Classes This lab will explore the java.util container classes Hashtable and Vector and the iterator Enumeration. Still using the library example, we now wish to index the documents to allow keyword search. Keywords will correspond to the categories covered by each document (science, politics, economy,..) One document can cover more than one category, and one category can be covered by several documents. In this lab we will only change the Library and Main classes. You can reuse all other classes (Document, Book, Deed, Magazine) from the previous lab. We want to be able to see the categories for a given document. Also we wish to retrieve, all the documents for a particular category, and this relationship should be favored in the implementation. The following is an example for the Main class. 1: import java.util.*; 2: 3: /** 4: * Main program. 6: * cases/library1/lab4 8: * $Id: Main.java,v /03/14 15:42:33 justb Exp $ 9: * <p> 10: * 11: $Author: justb $ Just van den Broecke Just Objects 12: */ 13: public class Main { 14: 15: public static void main(string args[]) { 16: 17: Library lib=new Library(); 18: Document doc; 19: 20: doc = new Book(10, "Hacking Java", 1500, "Mark Wutka", "QUE"); 21: lib.add(doc, "computing"); 22: 23: doc = new Magazine(30, "Java Report", 60, "monthly", "SIGS"); 24: lib.add(doc, "computingmags"); 25: 26: doc = new Deed(40, "A New Discovery in Science", 60, new Date(97, 0, 12)); 27: lib.add(doc, "science"); 28: 29: doc = new Book(50, "Making Money With Java", 1500, "Bill Gates", "Missy Press"); 30: Vector categories=new Vector(); 31: categories.addelement("computing"); 32: categories.addelement("economy"); 33: lib.add(doc, categories); 34: 35: System.out.println("=== START TEST 1 ==="); 36: lib.displaycontents("computing"); 37: System.out.println("=== END TEST 1 ==="); 38: 39: System.out.println("=== START TEST 2 ==="); 40: lib.displaycontents(); 41: System.out.println("=== END TEST 2 ==="); 42: 43: System.out.println("=== START TEST 3 ==="); 44: lib.displaycontents(doc); 45: System.out.println("=== END TEST 3 ==="); 46: } 47: } Rewrite the Library using the following skeleton (find this class under the 'exercises' dir). 4

7 1: import java.util.*; 2: 3: /** 4: * Library class with categories.. 6: * cases/library1/lab4 8: * $Id: Library.java,v /03/14 15:42:32 justb Exp $ 9: * <p> 10: * 11: $Author: justb $ Just van den Broecke Just Objects 12: */ 13: public class Library { 14: 15: // TODO: declare variables for collection classes 16: 17: 18: /** ctor: set up list of entries for each category. */ 19: public Library() { 20: // TODO: initialize collection classes 21: } 22: 23: /** Add document to single category. */ 24: public void add(document d, String category) { 25: // TODO: implement 26: } 27: 28: /** Add document to multiple categories. */ 29: public void add(document doc, Vector categories) { 30: // TODO: implement 31: } 32: 33: /** Display entire contents of library. */ 34: public void displaycontents() { 35: // TODO: implement 36: } 37: 38: /** Display contents for single category. */ 39: public void displaycontents(string category) { 40: // TODO: implement 41: } 42: 43: /** Display contents for single document; include all its categories. */ 44: public void displaycontents(document document) { 45: // TODO: implement 46: } 47: 48: /** Retrieves Documents for a given category. */ 49: public Vector retrievedocuments(string category) { 50: // TODO: implement 51: } 52: 53: /** Retrieves Vector of categories for a given Document. */ 54: public Vector retrievecategories(document document) { 55: // TODO: implement 56: } 57: } 5. Using Input/Output Streams This exercise explores classes in java.io. Addressed topics: Stream management I/O management Using classes BufferedReader, InputStreamReader, FileReader. Reading the standard input. Writing to a file. 5

8 Reusing the Document class, we would like the user to be prompted to type the title, id, and number of pages. We would also like to be able to save a Document object to a text file. 1. Use class BufferedReader to have the user type the document attributes. 2. Use classes OutputStreamWriter and FileWriter to save the object. Be sure that you catch any Exceptions. 3. Advanced: use serialization with ObjectOutputStream/ObjectInputStream to save/load a Document object in a file. 6. Advanced: Using Threads This exercise explores threads. Reuse the Library implementation from Lab4. Create a DocumentDisplayer class that extends Thread. Implement the run() method with an endless while loop in which performs the following tasks: 1. display library contents. 2. sleep 3 sekonds. Hint: use Thread.sleep() and be sure to catch InterruptedException. Start the DocumentDisplayer thread in Main.main(). End the program by typing control C. Advanced: Write a class called DocumentAdder that extends the java.lang.thread class. Implement the run() method with an endless while loop in which performs the following tasks: 1. sleep 6 sekonds. Hint: use Thread.sleep() and be sure to catch InterruptedException. 2. generate a random Document object (with a random, id, name and number of pages) and add it to the Library for a fixed category. The skeleton for DocumentAdder is given here. 1: /** 2: * Document adder thread.. 3: * <p> 4: * cases/library1/lab6 6: * $Id: DocumentAdder.java,v /03/14 15:42:33 justb Exp $ 8: * 9: $Author: justb $ Just van den Broecke Just Objects 10: */ 11: public class DocumentAdder extends Thread { 12: Library library; 13: String[] titles = {"Java", "More Java", "Excess Java", "Drown in Java"}; 14: String category = "computing"; 15: 16: /** Constructor with library reference. */ 17: DocumentAdder(Library thelibrary) { 18: library = thelibrary; 19: } 20: 21: /** Generate a random integer between min and max. */ 22: public int randomint(int min, int max) { 23: return (int) ((Math.random() * (double) (max+1 min))+min); 24: } 25: 26: /** Pick a random string from a given array of strings. */ 27: public String randomstring(string[] stringarray) { 28: return stringarray[randomint(0, stringarray.length 1)]; 29: } 30: 31: 32: /** Overridden from Thread. */ 33: public void run() { 6

9 34: // TODO implement 35: // sleep 6 sekonds 36: // create a random Document using randomint and randomstring(titles) 37: // add it to the library 38: } 39: 40: } Start the DocumentAdder and DocumentDisplayer threads in Main.main(). End the program by typing control C 7