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Sun Certified Developer for the Java 2 Platform: Application Submission

Introduction and Index

This document tells you what you should have, and what you should do, to submit your solution to the !!!Sun Certified Java Developer programming assignment. You should read it carefully before you begin work on the solution.

The application distribution consists of:

Be sure to maintain a backup copy of the distribution files until you receive your certificate in case one or more is corrupted, lost, or becomes unusable. You may not use files from sets issued to other certification candidates - even if you believe they are identical.

This document is broken down into the following sections:

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What This Application is About


Fly By Night Services is a small but growing travel agency that provides flight information on a small selection of routes and carriers. The company's IT department recently had an undergraduate student in for work experience during the summer vacation. This undergraduate did some work using the Java programming language and started to produce a rudimentary database system.

The Information Systems Department Manager now wishes to extend this work into a usable application. This application should keep scheduled flight information for a number of airlines and routes, and it should provide a convenient way to search for and book flights that might suit customer's requirements. This is the project that you have been commissioned to complete.

The Current Project Status

At present, a basic data storage and retrieval system (the "database") has been implemented and shown to work by the undergraduate. No network or user level code exists. The database is not relational. The data set for the project exists as a flat ASCII file, and it must be converted as part of the assignment. Fly By Night Services anticipates that future projects will use the same database and therefore this conversion program should be reasonably easy to reuse.

What you must do

The following are the "top level" features that must be implemented:

How you must do it

You have been given strict guidelines about the way the work is to be performed. These guidelines are to ensure consistency of marking and to ensure each candidate's workload is comparable.

The work involves a number of design choices that have to be made. In all such cases, the following principles should be applied.

Clarity and Maintainability.

A clear design, such as will be readily understood by junior programmers, will be preferred to a complex one, even if the complex one is a little more efficient than the simple choice. However, poor algorithm design where standard solutions are well known will be penalized.


The code itself should be as clear as possible, and "obvious" comments should be avoided. Awkward or complex code should have descriptive comments, and javadoc style comments must be used for each element of the public interface of each class. You must create a full suite of documentation for the classes of the completed project, including those that form part of this distribution. This must be achieved using the tool "javadoc" and must be in HTML format.

You should also provide basic user documentation. This should be sufficient to allow a user who is familiar with the intent of the project to use the application and conversion program. If you wish, appropriate parts of the user documentation may be provided on-line.


The design used must correctly implement the specified requirements.

Use of Standard Elements and Design Patterns.

The design should use standard Java package facilities wherever possible. Designs should not involve building new code if the effect can adequately be achieved using facilities in the standard Java packages. Performance alone is not a justification for ignoring this.

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Overall Architecture

Architecturally, the application is a traditional client-server system. There are three key parts: the server-side database with network server functionality, the client-side graphical user interface, and a client-side database client part that handles the networking on behalf of the user interface.

Additionally, the program must be able to work in a non-networked mode. In this mode, the database and user interface run in the same VM and no networking is performed. The user must be able to select the operating mode, although it is acceptable that the program stay in one mode once it has started up.

You have a choice regarding the network connection protocol. You may use either serialized objects over a simple socket connection, or you may use RMI. Your submission will fail automatically if you do not use one of these approaches.

The remote client code that you write must provide all the public methods of the suncertify.db.Data class.

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Supplied Code and Required Enhancements

The classes and code provided to you include some comments, including some in javadoc format. You should refer to these and consider the source itself for a full understanding of the provided code.

The following paragraphs outline the packages that are provided and detail the changes that you must make.

Deprecated Methods

In all packages, you should correct any use of deprecated methods. You will need to make some decisions about how to achive this. Consult the section What to do if you have a question which describes how you should approach this situation.

Target Platform

Throughout this exercise, you must use exclusively the Java 2 platform. This means that you should use a distribution of JDK 1.2 with its associated classes and tools. You are not required to develop your code using any particular implementation of the Java 2 platform, but the submission that you return must have been tested and shown to work under Sun Microsystems' reference version of the Java 2 platform.

Failure to adhere to these directions will result in automatic failure

Execution of Submissions

Your submission must run under the reference version of Sun's JRE 1.2. You may develop using an IDE (Integrated Development Environment) but your final product may not have any residual dependency upon that.

When you submit your assignment, you must ensure that it is packaged in such a way that it is completely clear how the examiner should run it using the reference JRE 1.2. Specifically, you should document clear, simple command lines that allow your programs to be run on any Java 2 platform, regardless of the underlying hardware and operating system. These command lines may only take configuration parameters selected from this list:

You must not require the editing of any files by the examiners.

Failure to adhere to these directions will result in automatic failure

Packaging of Submissions

All submissions must be packaged in a JAR file.

Database - Package suncertify.db

Following is a description of the package that is provided, and of the extensions you are expected to implement.

Three classes are in this package: Data, DataInfo, and FieldInfo. With the exception of three methods, noted below, these classes are complete and functional, and you have the source code for them. Any additional classes you create that are related to the database should be placed in the suncertify.db package.

Extending suncertify.db.Data

Part of your assignment will be to enhance the Data class. You may do this by modification or subclassing, but you should document the approach and reason for your choice.

You are required to implement the criteriaFind(String), lock(int) and unlock(int) methods:

public DataInfo[] criteriaFind(String criteria)

This method searches the database for entries matching the criteria supplied. Criteria take the form of a comma separated list of <field name>=<value to match> specifications.

For example, the following argument string would select all records describing flights by the SpeedyAir carrier that originate in San Francisco.


Note that only exact matches need to be handled in this criteriaFind(String) method.

The method returns an array of DataInfo objects describing all the records found in the database which match these criteria. In the event of an invalid field name being provided as part of the criteria the behavior of this method is the same as if no records matching correctly specified criteria.

public void lock(int record)

public void unlock(int record)

Record locking must be implemented using the methods public void lock(int) and public void unlock(int). These methods are required to allow concurrent use of the database when booking flights from multiple clients. Note that the locking required is effectively a "write" lock only. If updates occur to a record that is being displayed on another client, then no change occurs at the other client. However, if two clients attempt to perform the sequence lock,read,modify,write,unlock concurrently, then both modification attempts will be handled correctly. The aim is to ensure that if two customers attempt to book a seat on the same flight concurrently, then the number of available seats is definitely reduced by two, unless there was only one seat, in which case, one customer will be advised at booking time that no more seats are available.

The lock method should block until the requested lock can be applied. The integer argument indicates the record to be locked.

The unlock method simply removes the lock from the specified record. If an attempt is made to unlock a record that has not been locked by this connection, then no action is be taken.

Writing the Data Server

You must create a data server that will accept multiple concurrent network connections and allow them to interrogate and manipulate the database. Because multiple concurrent connections may exist, you must make both your server and the suncertify.db classes threadsafe. You may implement your threaded server in more than one class if you choose.

Writing Data Client

To connect with your server, you should create a client program. This implementation should include a class that implements the same public methods as the suncertify.db.Data class, although it will need different constructors to allow it to support the network configuration.

Creating the user interface

The user interface for this assignment must satisfy the following criteria:

Your user interface should be designed with the expectation of future functionality enhancements, and it should establish a control scheme that will support this with minimal disruption to the users when this occurs.

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Network Approaches

You may choose between using RMI, or using serialized objects over TCP socket connections, to implement the database network communication. Your choice here will not affect your grade, but no other approach is acceptable. In either case, the program must allow the user to specify the location of the database, and it must also accept an indication that a local database is to be used, in which case, the networking must be bypassed entirely. No authentication is required for database access.

You may implement such classes as you need in order to support this network protocol. The classes should be in appropriate packages and source files, and each method should be documented according to the general guidelines.

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The Data Conversion Tool

You must create a data conversion tool that reads the flat ASCII data file and creates a binary file for use by the suncertify.db.Data class.

This should be achieved bearing in mind that Fly By Night Services expects to make future use of this database and therefore expects to make use of the conversion tool for other projects in the future.

The conversion tool, along with its user documentation, must be provided as part of your project submission.

The Data Set

The data set provided is given here. You should copy this into an ascii file and use it for the project:


The format of this data is as follows. Fields are separated using the caret symbol '^':

You may modify the contents of the flat file, but such changes should be kept to a minimum and should only be made for a clearly justified reason.

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When you submit your assignment, you should provide the following parts.

All elements of your submission must be packaged into a single JAR file for submission. It is permitted to nest JAR files inside the main JAR.

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This section describes how your submission will be marked, and the marking criteria which govern allocation of marks for the Sun Certified Developer for the Java 2 platform application submission. The first part describes the marking process, and the second describes how the marks are allocated.

The first describes general criteria which are expected to apply to all parts of the submission. The second part is divided into three sections which describe considerations that are specific to the three main tasks in the requirements: the user interface, the network connection, and the database search facility.

How The Assignment is Marked

The marking is done is two phases. First, the examiner runs the code, ensuring that it functions correctly through the specified operations.

Provided the essential behavioral requirements of the assignment have been correctly implemented, the examiner proceeds to investigate the design and implementation of your assignment. This process is time consuming, and it is because this is done carefully and thoroughly that submissions take time to grade. The grading process is closely controlled to ensure consistency and fairness, and it is performed according to criteria detailed in the next section.

In addition to the submission, you will be required to take a written examination. This exam tests your understanding of your submission and asks you to justify a number of design choices embodied in that submission. For any design choice concerning topics not specifically described in the requirements, marks are awarded for a clear and consistent approach, rather than for any particular solution. Design decisions should be briefly but clearly described in your comments.

Marking Criteria

The following marking criteria are given as a guide. The numbers in parentheses beside each topic indicate the relative proportion of marks available in that area (note that they do not add up to 100, and hence are not percentages). Some of these criteria, especially the ones in "General Considerations," apply in more than one place, and as such might appear to show a disproportionate score. In some cases, a topic shows a few notes to elaborate on the meaning of the heading.

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What to do if you have a question

You may find that you want to ask for further explanation of some part of these notes, perhaps to seek permission to solve a problem in a particular way. These notes deliberately leave some issues unspecified, and some problems unraised. Your ability to think through these issues, in the face of realistically imperfect specifications, and come to a tenable solution is something upon which you are being graded.

You should consider the options available and make a decision about how to address the problem yourself. This decision making process is part of the marking scheme, and as such it is crucially important that you provide documentation of your choice. Be sure to describe the options you considered, the perceived benefits and weaknesses of each, and why you chose the solution you did. You will not be marked on the choice that you made, but rather on the consistency of your decision making process and your adherence to other aspects of these notes during that decision making process.

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