BBM104 Assignment 3-Inheritance and Polimorphism Solved

1 Introduction

In this experiment, you have been commissioned to develop a hospital management system (HMS). You are expected to implement HMS with the given rule. The main focus of this experiment is to get you familiar with inheritence and polymorphism concepts in object oriented (OO) programming.

Inheritance is one of the core concepts of object-oriented programming (OOP). It is a mechanism where you can to derive a class from another class for a hierarchy of classes that share a set of attributes and methods.

Polymorphism is the ability of an object to take on many forms. The most common use of polymorphism in object oriented design occurs when a parent class reference is used to refer to a child class object.

It is expected you to implement the program by using inheritence and polimorphism. Imple- menting the program without using the benefits of these concepts will be penalized.

Figure 1: Hospital Management System

2 Problem

In this experiment you are expected to implement a hospital management system. The aim of this experiment is to introduce you object-oriented programming and design with Java. You will learn the structure of a class, how classes interact, inheritance and polymorphism and basic input-output operations in Java. There will be two main parts to this assignment.

• One part consists of creating the system’s input-output interface and implementing the logic for this interaction. You should also use decorator design pattern in this part of

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the experiment.

• The other part is defining (and implementing) the persistence backend (i.e. how we store and retrieve the information our system uses).

Your program will take commands from an input file then it will print the results of these commands to an output file. You should use Data Access Objects (DAO) to manage your data.

2.1 Decorator Pattern

The Java language provides the keyword extends for subclassing a class. By extending a class, you can change its behavior. The Decorator Pattern is used for adding additional functionality to a particular object as opposed to a class of objects. With the Decorator Pattern, you can add functionality to a single object and leave others like it unmodified. Any calls that the decorator gets, it relays to the object that it contains, and adds its own functionality along the way, either before or after the call. This gives you a lot of flexibility since you can change what the decorator does at runtime, as opposed to having the change to be static and determined at compile time by subclassing. Since a Decorator complies with the interface that the object that it contains, the Decorator is indistinguishable from the object that it contains. That is, a Decorator is a concrete instance of the abstract class, and thus is indistinguishable from any other concrete instance, including other decorators. This can be used to great advantage, as you can recursively nest decorators without any other objects being able to tell the difference, allowing a near infinite amount of customization. Decorators add the ability to dynamically alter the behavior of an object because a decorator can be added or removed from an object without the client realizing that anything changed. It is a good idea to use a Decorator in a situation where you want to change the behavior of an object repeatedly (by adding and subtracting functionality) during runtime.

Figure 2: A sample UML class and sequence diagram for the Decorator design pattern

The dynamic behavior modification capability also means that decorators are useful for adapt- ing objects to new situations without re-writing the original object’s code.

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2.2 Data Access Object

The Data Access Object (DAO) layer is an essential part of good application architecture. Business applications almost always need access to data from databases or data files. The Data Access Object design pattern provides a technique for separating object persistence (stored data) and data access logic from any particular persistence mechanism (writing to files or accessing a real database). There are clear benefits to this approach from an ar- chitectural perspective. The Data Access Object approach provides flexibility to change an application’s persistence mechanism over time without the need to re-engineer application logic that interacts with the Data Access Object tier. The Data Access Object design pattern also provides a simple, consistent API for data access that does not require knowledge of sub mechanism. A typical Data Access Object class diagram is shown below. (This is an example, your interface should look like different).

Figure 3: A sample UML class diagram

3 Experiment Details

In this experiment, you are expected to develop a simple Hospital Management System. Your application should support the following features:

• New Patient: Create a new patient. Attributes of a patient are: – patient id (Unique)
  – patient surname
  – patient name

  – patient address

  – patient phone number

• Remove Patient:

  Remove a patient from the database by using its identification number.

• List Patients:
  Print the list of patients ordered by name.
• Create Admission:
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Create a new admission for an existing patient and append it to admission data file. Each admission has a unique admission id.

• Add Examination: Add an examination to a given order with given operations. An examination can include 3 operations at most. There are 2 types of examination. These are:

• –  Inpatient examination 10 $
• –  Outpatient examination 15 $
  An examination can include 3 additional operations at most. There are 4 types of

  operations:
  – doctor visit 15 $ – imaging 10 $
  – tests 7 $
  – measurements 5 $

  • Total Cost
  Calculate the total cost of an admission. List all examinations in the order then calculate

  the total cost of an admission.

  Patient information and admission information will be stored in text files. The format of the files for persistence are shown below. You can reach sample patient file, admission data file and sample input-output files from the page of piazza site of the experiment.

3.1 Patient Data File Format:

< patientID > tab < patientName > space < patientSurname > tab < phone number > tab < address > newline

Patient name and surname consist of one string. The address can be made up of one or more strings. Entries in patient data file should be ordered by ID. After add and remove operations, all changes should be reflected to data files (patient.txt ve admission.txt). In Figure 4, you can see an example of patient.txt file.

Figure 4: A sample patient.txt file

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3.2 Admission Data File Format:

< admissionID > tab < patientID > newline
< examination type(InpatientorOutpatient) > tab < operation [1-4] >

Entries in admission data file should be ordered by ID. After add and remove operations, all changes should be reflected data files. In Figure 5, you can see a sample admission.txt file.

Figure 5: A sample admission.txt file

3.3 Input File Format

(Note: Number of operations can vary from 1 to 3.)

• AddPatient space < patientID > space < name > space < surname >< phone number >

  space < address >

• RemovePatient space < patient ID >
• CreateAdmission space < AdmissionID > space < PatientID >
• AddExamination space < AdmissionID > space < examination type > space < operation >
• TotalCost space < AdmissionID >
• ListPatients

Figure 6: A sample input.txt file

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3.4 Output File Format

• Patient < PatientID >< name > added
• Patient < PatientID >< name > removed
• Admission < AdmissionID > created
• < Examinationtype > examination added to admission < AdmissionID > • Total cost for admission < AdmissionID >

– < examinationtype >< operation[1 − 4] >< cost > – < examinationtype >< operation[1 − 4] >< cost > – Total: < total cost >

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Figure 7: A sample output.txt file

Implementation Details

You have to use decorator pattern (20points) for adding operations mechanism. Add operation code should look like this:

examination.addoperation(new imaging(new test(new measurement())); This an examination with imaging, test, and measurement.

examination.printoperations(); Output of this method call should be measurement, test and imaging

examination.cost(); Output of this method call should return the costs of examination and its operations

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BBM104: Introduction to Programming Laboratory II (Spring 2020)

For our system, we will store the data inside the individual files (one for admission and one for patient class), and use Data Access Objects (DAO) to manage them (10points). Each DAO will have the basic operations to manage the data (defined by the DAO interface provided with the assignment). So basically what you need to do is implementing following abstract methods:

Object getByID(int ID) // read a single entry from the file Object deleteByID(int ID) // delete a single entry from file void add(Object object) // add or update an entry ArrayList getALL() // get all entries

You could add additional methods to your DAOs and you can also make changes in DAO interface. Your application should terminate and save the files automatically when finish to read the input file.

5 Execution and Test

The input file (input.txt) is going to be given as program arguments. There are text files (patient.txt, admission.txt) in your working directory and when your program starts, you will read these files, then update them according to the input file. In order to test your program, you should follow the following steps:

• Upload your java files to your server account (dev.cs.hacettepe.edu.tr) • Compile your code (javac *.java)
• Run your program (java Main input.txt)
• Control your output data (output.txt).