Question

ANNOTATE BRIEFLY LINE BY LINE THE FOLLOWING CODE:

package shop.data;

import junit.framework.Assert;
import junit.framework.TestCase;

public class DataTEST extends TestCase {
public DataTEST(String name) {
super(name);
}
public void testConstructorAndAttributes() {
String title1 = "XX";
String director1 = "XY";
String title2 = " XX ";
String director2 = " XY ";
int year = 2002;

Video v1 = Data.newVideo(title1, year, director1);
Assert.assertSame(title1, v1.title());
Assert.assertEquals(year, v1.year());
Assert.assertSame(director1, v1.director());

Video v2 = Data.newVideo(title2, year, director2);
Assert.assertEquals(title1, v2.title());
Assert.assertEquals(director1, v2.director());
}

public void testConstructorExceptionYear() {
try {
Data.newVideo("X", 1800, "Y");
Assert.fail();
} catch (IllegalArgumentException e) { }
try {
Data.newVideo("X", 5000, "Y");
Assert.fail();
} catch (IllegalArgumentException e) { }
try {
Data.newVideo("X", 1801, "Y");
Data.newVideo("X", 4999, "Y");
} catch (IllegalArgumentException e) {
Assert.fail();
}
}

public void testConstructorExceptionTitle() {
try {
Data.newVideo(null, 2002, "Y");
Assert.fail();
} catch (IllegalArgumentException e) { }
try {
Data.newVideo("", 2002, "Y");
Assert.fail();
} catch (IllegalArgumentException e) { }
try {
Data.newVideo(" ", 2002, "Y");
Assert.fail();
} catch (IllegalArgumentException e) { }
}

public void testConstructorExceptionDirector() {
}

}

package shop.data;

import java.util.Map;
import java.util.HashMap;
import java.util.Comparator;
import java.util.Collections;
import java.util.List;
import java.util.ArrayList;
import java.util.Iterator;
import shop.command.Command;
import shop.command.UndoableCommand;
//import shop.data.InventorySet.RecordObj;
import shop.command.CommandHistory;
import shop.command.CommandHistoryFactory;
import shop.command.CommandHistoryObj;

/**
* Implementation of Inventory interface.
* @see Data
*/
final class InventorySet implements Inventory {
private Map<Video,Record> _data;
private final CommandHistory _history;

InventorySet() {
_data = new HashMap<Video,Record>();
_history = new CommandHistoryObj();

}

/**
* If <code>record</code> is null, then delete record for <code>video</code>;
* otherwise replace record for <code>video</code>.
*/
void replaceEntry(Video video, Record record) {
_data.remove(video);
if (record != null)
_data.put(video,((RecordObj)record).copy());
}

/**
* Overwrite the map.
*/
void replaceMap(Map<Video,Record> data) {
_data = data;
}

public int size() {
// TODO
return _data.size();
}

public Record get(Video v) {
// TODO
return _data.get(v);
}

public Iterator<Record> iterator() {
return Collections.unmodifiableCollection(_data.values()).iterator();
}

public Iterator<Record> iterator(Comparator<Record> comparator) {
   List<Record> res = new ArrayList<Record>(_data.values());
   Collections.sort(res, comparator);
   return Collections.unmodifiableCollection(res).iterator();
}

/**
* Add or remove copies of a video from the inventory.
* If a video record is not already present (and change is
* positive), a record is created.
* If a record is already present, <code>numOwned</code> is
* modified using <code>change</code>.
* If <code>change</code> brings the number of copies to be less
* than one, the record is removed from the inventory.
* @param video the video to be added.
* @param change the number of copies to add (or remove if negative).
* @return A copy of the previous record for this video (if any)
* @throws IllegalArgumentException if video null or change is zero
*/
Record addNumOwned(Video video, int change) {
if (video == null || change == 0)
throw new IllegalArgumentException();
  
RecordObj r = (RecordObj) _data.get(video);
if (r == null && change < 1) {
throw new IllegalArgumentException();
} else if (r == null) {
_data.put(video, new RecordObj(video, change, 0, 0));
} else if (r.numOwned+change < r.numOut) {
throw new IllegalArgumentException();
} else if (r.numOwned+change < 1) {
_data.remove(video);
} else {
_data.put(video, new RecordObj(video, r.numOwned + change, r.numOut, r.numRentals));
}
return r;
}

/**
* Check out a video.
* @param video the video to be checked out.
* @return A copy of the previous record for this video
* @throws IllegalArgumentException if video has no record or numOut
* equals numOwned.
*/
Record checkOut(Video video) {
   RecordObj r = (RecordObj) _data.get(video);
  
   if (r==null || r.numOut == r.numOwned)
       throw new IllegalArgumentException();
  
   _data.put(video, new RecordObj(video, r.numOwned, r.numOut+1, r.numRentals+1));
   return r;
}
  
/**
* Check in a video.
* @param video the video to be checked in.
* @return A copy of the previous record for this video
* @throws IllegalArgumentException if video has no record or numOut
* non-positive.
*/
Record checkIn(Video video) {
   RecordObj r = (RecordObj) _data.get(video);
  
   if (r==null || r.numOut==0)
       throw new IllegalArgumentException();
  
   _data.put(video, new RecordObj(video, r.numOwned, r.numOut-1, r.numRentals));
   return r;
}
  
/**
* Remove all records from the inventory.
* @return A copy of the previous inventory as a Map
*/
Map clear() {
// TODO
   Map<Video,Record> v = _data;
   _data = new HashMap<Video,Record>();
   return v;
}

/**
* Return a reference to the history.
*/
CommandHistory getHistory() {
// TODO
return _history;
}
  
public String toString() {
StringBuffer buffer = new StringBuffer();
buffer.append("Database:\n");
Iterator i = _data.values().iterator();
while (i.hasNext()) {
buffer.append(" ");
buffer.append(i.next());
buffer.append("\n");
}
return buffer.toString();
}

/**
* Implementation of Record interface.
*
* <p>This is a utility class for Inventory. Fields are mutable and
* package-private.</p>
*
* <p><b>Class Invariant:</b> No two instances may reference the same Video.</p>
*
* @see Record
*/
private static final class RecordObj implements Record {
Video video; // the video
int numOwned; // copies owned
int numOut; // copies currently rented
int numRentals; // total times video has been rented
  
RecordObj(Video video, int numOwned, int numOut, int numRentals) {
this.video = video;
this.numOwned = numOwned;
this.numOut = numOut;
this.numRentals = numRentals;
}
RecordObj copy() {
return new RecordObj(video, numOwned, numOut, numRentals);
}
public Video video() {
return video;
}
public int numOwned() {
return numOwned;
}
public int numOut() {
return numOut;
}
public int numRentals() {
return numRentals;
}
public boolean equals(Object thatObject) {
return video.equals(((Record)thatObject).video());
}
public int hashCode() {
return video.hashCode();
}
public String toString() {
StringBuffer buffer = new StringBuffer();
buffer.append(video);
buffer.append(" [");
buffer.append(numOwned);
buffer.append(",");
buffer.append(numOut);
buffer.append(",");
buffer.append(numRentals);
buffer.append("]");
return buffer.toString();
}
}

Answer 1

// Adding comment for each line
// DataTEST class is in package shop.data, so it can be referred as shop.data.DataTEST
package shop.data;

// importing the Assert and TestCase class of junit library
import junit.framework.Assert;
import junit.framework.TestCase;

// DataTEST class is extending the TestCase class of junit library,
// so it can access all members of the TestCase class
public class DataTEST extends TestCase {

// Below is the custom constructor of the DataTEST class which takes string as a argument
public DataTEST(String name) {
//calls to its parent(TestCase) constructor with string parameter
super(name);
}

// test method for validating the constructor and it its attributes
public void testConstructorAndAttributes() {
// creating and assinging values to String variables
String title1 = "XX";
String director1 = "XY";
String title2 = " XX ";
String director2 = " XY ";
// creating new int variable
int year = 2002;

// creating new instatnce of type video by passing 3 parameter to newVideo() method of Data class.
Video v1 = Data.newVideo(title1, year, director1);

// it will check if both the parameter are same, in below case they are same so it will fail
Assert.assertSame(title1, v1.title());

// it will check if both the parameter are equal, in below case they are equal so it will fail
Assert.assertEquals(year, v1.year());

// it will check if both the parameter are same, in below case they are same so it will fail
Assert.assertSame(director1, v1.director());

// creating new instatnce of type video by passing 3 parameter to newVideo() method of Data class.
Video v2 = Data.newVideo(title2, year, director2);
// it will check if both the parameter are equal, in below case they are not equal so it will pass
Assert.assertEquals(title1, v2.title());
// it will check if both the parameter are equal, in below case they are not equal so it will pass
Assert.assertEquals(director1, v2.director());
}

// test method for validating the year argument of constructor
public void testConstructorExceptionYear() {
// try block starts
try {
// calling newVideo method of Data class
Data.newVideo("X", 1800, "Y");
//The Assert.Fail method provides you with the ability to generate a failure based on tests
// that are not encapsulated by the other methods
Assert.fail();
}
// catch block will be executed if IllegalArgumentException is thrown by catch block
catch (IllegalArgumentException e) {
// catch block will nothing
}
try {
Data.newVideo("X", 5000, "Y");
Assert.fail();
}
// catch block will be executed if IllegalArgumentException is thrown by catch block
catch (IllegalArgumentException e) { }
try {
Data.newVideo("X", 1801, "Y");
Data.newVideo("X", 4999, "Y");
}
// catch block will be executed if IllegalArgumentException is thrown by catch block
catch (IllegalArgumentException e) {
// catch block, if executed will fail the execution
Assert.fail();
}
}

// test method for validating the Title argument of constructor
public void testConstructorExceptionTitle() {
try {
// passing null value for title parameter to constructor
Data.newVideo(null, 2002, "Y");
Assert.fail();
}
// catch block will be executed if IllegalArgumentException is thrown by catch block
catch (IllegalArgumentException e) { }
try {
// passing empty string value for title parameter to constructor
Data.newVideo("", 2002, "Y");
Assert.fail();
} catch (IllegalArgumentException e) { }
try {
// passing space value for title parameter to constructor
Data.newVideo(" ", 2002, "Y");
Assert.fail();
} catch (IllegalArgumentException e) { }
}

// empty method which will do nothing if called
public void testConstructorExceptionDirector() {
}

}

package shop.data;

// importing util library classes
import java.util.Map;
import java.util.HashMap;
import java.util.Comparator;
import java.util.Collections;
import java.util.List;
import java.util.ArrayList;
import java.util.Iterator;
// importing classes of shop package
import shop.command.Command;
import shop.command.UndoableCommand;
//import shop.data.InventorySet.RecordObj;
import shop.command.CommandHistory;
import shop.command.CommandHistoryFactory;
import shop.command.CommandHistoryObj;

/**
* Implementation of Inventory interface.
* @see Data
*/
final class InventorySet implements Inventory {
// creating map of Video as key and Record as value
private Map<Video,Record> _data;
// creating final variable
private final CommandHistory _history;

// constructor of the class which is setting the instance variable
InventorySet() {
_data = new HashMap<Video,Record>();
_history = new CommandHistoryObj();

}

/**
* If <code>record</code> is null, then delete record for <code>video</code>;
* otherwise replace record for <code>video</code>.
*/
void replaceEntry(Video video, Record record) {
_data.remove(video);
if (record != null)
_data.put(video,((RecordObj)record).copy());
}

/**
* Overwrite the map.
*/
void replaceMap(Map<Video,Record> data) {
_data = data;
}

public int size() {
// return the size of _data map
return _data.size();
}

public Record get(Video v) {
// return record from _data map having key as the parameter
return _data.get(v);
}

// return Iterator for Record list which are present in the _data map
public Iterator<Record> iterator() {
return Collections.unmodifiableCollection(_data.values()).iterator();
}

// return Iterator for sorted Record list of Record objects which are present in the _data map
public Iterator<Record> iterator(Comparator<Record> comparator) {
List<Record> res = new ArrayList<Record>(_data.values());
Collections.sort(res, comparator);
return Collections.unmodifiableCollection(res).iterator();
}

/**
* Add or remove copies of a video from the inventory.
* If a video record is not already present (and change is
* positive), a record is created.
* If a record is already present, <code>numOwned</code> is
* modified using <code>change</code>.
* If <code>change</code> brings the number of copies to be less
* than one, the record is removed from the inventory.
* @param video the video to be added.
* @param change the number of copies to add (or remove if negative).
* @return A copy of the previous record for this video (if any)
* @throws IllegalArgumentException if video null or change is zero
*/
Record addNumOwned(Video video, int change) {
if (video == null || change == 0)
throw new IllegalArgumentException();
  
RecordObj r = (RecordObj) _data.get(video);
if (r == null && change < 1) {
throw new IllegalArgumentException();
} else if (r == null) {
_data.put(video, new RecordObj(video, change, 0, 0));
} else if (r.numOwned+change < r.numOut) {
throw new IllegalArgumentException();
} else if (r.numOwned+change < 1) {
_data.remove(video);
} else {
_data.put(video, new RecordObj(video, r.numOwned + change, r.numOut, r.numRentals));
}
return r;
}

/**
* Check out a video.
* @param video the video to be checked out.
* @return A copy of the previous record for this video
* @throws IllegalArgumentException if video has no record or numOut
* equals numOwned.
*/
Record checkOut(Video video) {
RecordObj r = (RecordObj) _data.get(video);
  
if (r==null || r.numOut == r.numOwned)
throw new IllegalArgumentException();
  
_data.put(video, new RecordObj(video, r.numOwned, r.numOut+1, r.numRentals+1));
return r;
}
  
/**
* Check in a video.
* @param video the video to be checked in.
* @return A copy of the previous record for this video
* @throws IllegalArgumentException if video has no record or numOut
* non-positive.
*/
Record checkIn(Video video) {
RecordObj r = (RecordObj) _data.get(video);
  
if (r==null || r.numOut==0)
throw new IllegalArgumentException();
  
_data.put(video, new RecordObj(video, r.numOwned, r.numOut-1, r.numRentals));
return r;
}
  
/**
* Remove all records from the inventory.
* @return A copy of the previous inventory as a Map
*/
Map clear() {
// TODO
Map<Video,Record> v = _data;
_data = new HashMap<Video,Record>();
return v;
}

/**
* Return a reference to the history.
*/
CommandHistory getHistory() {
// return _history instance variable of class
return _history;
}
  
// overriding the toString() method of Java.lang.Object
public String toString() {
// creating string buffer variable
StringBuffer buffer = new StringBuffer();
// append Database in the string buffer
buffer.append("Database:\n");
// creating iterator for the list of Record objects which are present in the _data map
Iterator i = _data.values().iterator();
// appending space
while (i.hasNext()) {
// appending space in buffer
buffer.append(" ");
// appending value of record objects from the list in buffer
buffer.append(i.next());
// appending new line in buffer
buffer.append("\n");
}
// return the string value of buffer
return buffer.toString();
}

/**
* Implementation of Record interface.
*
* <p>This is a utility class for Inventory. Fields are mutable and
* package-private.</p>
*
* <p><b>Class Invariant:</b> No two instances may reference the same Video.</p>
*
* @see Record
*/
private static final class RecordObj implements Record {
Video video; // the video
int numOwned; // copies owned
int numOut; // copies currently rented
int numRentals; // total times video has been rented
  
// constructor for the RecordObj class
RecordObj(Video video, int numOwned, int numOut, int numRentals) {
this.video = video;
this.numOwned = numOwned;
this.numOut = numOut;
this.numRentals = numRentals;
}
RecordObj copy() {
return new RecordObj(video, numOwned, numOut, numRentals);
}
public Video video() {
return video;
}
public int numOwned() {
return numOwned;
}
public int numOut() {
return numOut;
}
public int numRentals() {
return numRentals;
}
// overriding the equals method of java.lang.object
public boolean equals(Object thatObject) {
return video.equals(((Record)thatObject).video());
}
// overriding the hashCode method of java.lang.object
public int hashCode() {
return video.hashCode();
}
// overriding the toString method of java.lang.object
// it returns the string containing values of all the instance variable
public String toString() {
StringBuffer buffer = new StringBuffer();
buffer.append(video);
buffer.append(" [");
buffer.append(numOwned);
buffer.append(",");
buffer.append(numOut);
buffer.append(",");
buffer.append(numRentals);
buffer.append("]");
return buffer.toString();
}
}