CS 596: Client-Server Programming
Spring Semester, 1997
Doc 8, Assignment 1 Comments
To Lecture Notes Index
San Diego State University -- This page last updated Feb 18, 1997
Contents of Doc 8, Assignment 1 Comments
| Static Problem | slide # 1 |
| |
| Constant Problem | slide # 2 |
| |
| Print Problem | slide # 3 |
| |
| Struct Problem | slide # 4 |
| |
| The God Class Problem | slide # 5 |
| |
| Classes in One File | slide # 8 |
| |
| No Data Files | slide # 9 |
| |
| Continually Reading Data Files | slide # 10 |
| |
| Exception Problem | slide # 11 |
| |
| Singleton Problem | slide # 12 |
| |
| Documentation Problem | slide # 13 |
| |
| Positional Data Problem | slide # 18 |
Static Problem
class AirlineSchedule
{
private static Table data
public static void doSomething()
{ blah }
public static void methodA()
{blah}
}
class Cities
{
private static SomeType ModeData
public static void methodC()
{blah }
public static void methodB()
{blah}
}
Constant Problem
class AirlineSchedule
{
private String scheduleFile = "schedule";
private Table data;
public AirlineSchedule()
{
InputStream cin = new FileInputStream( scheduleFile);
blah blah
}
public void seatsOnPlane( String planeType)
{
if ( planeType == "A")
return 5;
else if ( planeType.equals( "B" ) )
return 10;
else if ( planeType.equals( "C" ) )
return 15;
}
}
Print Problem
class AirlineSchedule
{
Hashtable cityAndCodes;
public void citiesServed_BadNews()
{
Enumeration cities = cityAndCodes.keys();
while ( cities.hasMoreElements() )
System.out.print( cities.nextElement() );
System.out.println();
}
public void citiesServed_Better(OutputStream output)
{
Enumeration cities = cityAndCodes.keys();
while ( cities.hasMoreElements() )
output.print( cities.nextElement() );
output.println();
}
public Vector citiesServed_BetterYet()
{
Enumeration cities = cityAndCodes.keys();
Vector cityList = new Vector();
while ( cities.hasMoreElements() )
cityList.addElement( cities.nextElement() );
return cityList;
}
}
Struct Problem
class Flight
{
int flightNumber;
String originCity;
String destinationCity;
String planeType;
public void setOriginCity( String newValue )
{originCity = newValue; }
public getOriginCity( )
{return originCity;}
public void setDestinationCity( String newValue ) {blah }
public getDestinationCity( ) {blah}
public void setPlaneType( String newValue ) {blah }
public getPlaneType( ) {blah}
public void setFlightNumber( String newValue ) {blah }
public getFlightNumber( ) {blah}
}
The God Class Problem
class AirlineSchedule
{
public String getManifest()
{
blah
blah
blah
blah
while ( blah )
{
blah
blah
blah
blah
if ( blah )
blah
else
{
blah
blah
blah
blah
}
blah
}
blah
blah
blah
blah
blah
do
The God Class Problem
{
blah
blah
blah
blah
blah
try
{
blah
blah
blah
}
catch ( blah )
{
blah
}
}
until ( blah )
blah
blah
blah
blah
switch ( blah )
{
blah
blah
blah
}
return blah;
}
File Problem 1
Classes in One File
file: p1.java
class Flight
{
BLAH
}
class AirlineSchedule
{
BLAH
}
class Cities
{
BLAH
}
class Reservations
{
BLAH
}
File Problem 2
No Data Files
class AirlineSchedule
{
private String scheduleFile = "schedule";
private Table data;
public AirlineSchedule()
{
InputStream cin = new FileInputStream( scheduleFile);
blah blah
}
public void seatsOnPlane( String planeType)
{
if ( planeType == "A")
return 5;
else if ( planeType.equals( "B" ) )
return 10;
else if ( planeType.equals( "C" ) )
return 15;
}
}
File Problem 3
Continually Reading Data Files
public String getManifest( in FlightNumber, Date ofFlight)
{
InputStream cin = new FileInputStream( reservations);
read to correct line in file
String manifest = cin.readLine();
cin.close();
return manifest
}
public String getCityList()
{
InputStream cin = new FileInputStream( cities);
read to correct line in file
String cityList = cin.readLine();
cin.close();
return cityList;
}
Exception Problem
class AirlineSchedule
{
private String scheduleFile = "schedule";
private LabeledData data;
public loadFile()
{
try
{
InputStream cin = new FileInputStream( scheduleFile);
LabeledData.load( cin );
}
catch ( FileNotFoundException noFile )
{
System.out.println( "Could not find file" );
}
}
Singleton Problem
// Only one object of this class should exist in the program
class IForgetWhatClassTheyDidThisIn
{
blah
}
// Only one object of this class can be created
class SingleObject
{
private SingleObject instance = null;
private SingleObject()
{ blah }
public static SingleObject getInstance()
{
if ( instance == null )
instance = new SingleObject();
return instance;
}
}
Documentation Problem 1
| Comments | none | some | not useful | useful |
| Document | XX | | | |
| Class | XX | | | |
| Method | XX | | | |
| Inline | XX | | | |
| Java Doc | XX | | | |
| Comments | none | some | not useful | useful |
| Document | XX | | | |
| Class | | XX | XX | |
| Method | | XX | XX | |
| Inline | XX | | | |
| Java Doc | XX | | | |
Documentation Problem 2
"Table class, what Table class? You didn't tell us about that!"
Sample Use of Table
class Reservations
{
Table reservationData;
String reservationFileName;
public static void newDataBase( String fileName ) throws
FileExistsException, IOException
{
if ( new File( fileName ).exists() )
throw new FileExistsException( fileName );
OutputStream cout = new BufferedOutputStream (
new FileOutputStream( fileName ) );
Table dataBase = new Table();
Vector header = new Vector();
header.addElement( "Name");
header.addElement( "FlightNumber");
header.addElement( "Date");
dataBase.addRow( header );
String nullMessage = null;
dataBase.save( cout, nullMessage );
cout.flush();
cout.close();
}
Reservations # 2
public Reservations( String fileName) throws
FileNotFoundException, IOException
{
reservationFileName = fileName;
reservationData = new Table();
InputStream cin = new BufferedInputStream (
new FileInputStream( fileName ) );
reservationData.load( cin );
cin.close();
}
public int seatsFilled( String flightNumber, String date )
{
return flightManifest( flightNumber, date ).numberOfRows();
}
public boolean hasReservation( String name,
String flightNumber,
String date )
{
Table flightManifest = flightManifest( flightNumber, date );
return flightManifest.contains( name );
}
public void makeReservation( String name,
String flightNumber,
String date ){
Vector passengerData = new Vector();
passengerData.addElement(name);
passengerData.addElement(flightNumber);
passengerData.addElement(date);
reservationData.addRow( passengerData );
}
Reservations # 3
public Table flightManifest( String flightNumber, String date )
{
Table flightData = reservationData.rowsAt( flightNumber, 1);
return flightData.rowsAt( date, 2 );
}
public void saveReservations() throws IOException
{
OutputStream cout = new BufferedOutputStream (
new FileOutputStream(
reservationFileName ) );
String nullMessage = null;
reservationData.save( cout, nullMessage );
cout.flush();
cout.close();
}
}
class FileExistsException extends Exception
{
public FileExistsException()
{ super(); }
public FileExistsException( String message )
{ super(message); }
}
Positional Data Problem
Variation 5
| From | To | DepartTime | ArrivalTime | FlightNumber | AircraftType |
| AMS, | LAX, | 04:15, | 15:15, | 602, | C; |
static final int CITY_TO_COLUMN = 1;
static final int CITY_FROM_COLUMN = 0;
static final int ARRIVAL_TIME_COLUMN = 3;
static final int DEPARTURE_TIME_COLUMN = 2;
static final int FLIGHT_NUMBER_COLUMN = 4;
static final int AIRCRAFT_TYPE_COLUMN = 5;
Table schedule;
public string getArrivalTime( String FlightNumber )
{
Table myFlight = schedule.rowsAt( FlightNumber,
FLIGHT_NUMBER_COLUMN);
return myFlight.elementAt( 2, ARRIVAL_TIME_COLUMN );
}
in Table class (in case you haven't seen the table class)
/**
* Returns a new table containing all the rows that have the value
* "key" in the indicated column
*/
public Table rowsAt( Object key, int column )
Positional Data Problem
Variation 5 - Solution
| From | To | DepartTime | ArrivalTime | FlightNumber | AircraftType |
| AMS, | LAX, | 04:15, | 15:15, | 602, | C; |
class AirlineSchedule
{
Table schedule;
Vector columnIndex;
public AirlineSchedule()
{
blah
schedule.load( scheduleInputStream );
columnIndex = schedule.rowAt( 0 );
}
public string getArrivalTime( String FlightNumber )
{
Table myFlight;
myFlight = schedule.rowsAt( FlightNumber,
columnIndex.indexOf( "FlightNumber"
));
return myFlight.elementAt( 2,
columnIndex.indexOf( "ArrivalTime")
);
}
Positional Data Problem
Variation 5 - A Better Solution
Stop writing programs
Build classes to use in programs
Then write programs
class LabeledTable extends Table
{
public Table rowsAt( Object key, String columnLabel )
{
int columnNumber = getColumnIndex( columnLabel );
return super.rowsAt( key, columnNumber );
}
}
