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日期:2021-07-22 07:35

COSI 12B – Advanced Programming Techniques

Programming Assignment 4

Objective

Practice developing a well encapsulated object-oriented program

Practice using Eclipse Debugger Tool

Overview

In this assignment, you will be simulating a building that contains a single

elevator. However, this elevator has a special characteristic, it can only be used

once by a person as they enter the building. Once someone has used the elevator

they will remain at their floor forever. You can think of this elevator as a one-

way elevator.


Person instances will request to enter the building and go to a specific floor.

Two things need to happen. As a person arrives at the building, the elevator may

or may not be on the first floor, ready to take new passengers. To address this

problem, we will put a “job” on the elevator to go to floor number 1, and

immediately after put a second “job” for the person that has entered the building

to go the their desired floor. More is said about this further on.

This elevator will not be very efficient, since it will process “jobs” in order

(first-come-first- serve). So, if two people come to the building, the elevator will

come to the first floor, take the first person and then take them to their desired

floor, and then go back to the first floor for the second person that entered the

building. The elevator is given a batch of “jobs” and then it should process the

entire batch as fast as possible.

You will be coding an Object-Oriented solution, where you will need to

implement the following classes:

Building: It should hold an array of floors and an instance of an elevator.

Floor: Every floor must contain an array of people (that are currently on a given

floor). ?

Elevator: An elevator will contain a list of Jobs (as an array), where each Job

represents a person and the floor to which they desire to go. The elevator should

also contain a?reference to the building to which it belongs. ?

Person: Each person has a first name and a last name.

Job: This class is used to represent an elevator trip. This class holds a reference

to a Person and a floor number. You can use a null object for the first parameter

to represent an empty trip (calling the elevator to the first floor). ?

Simulation: This class should contain a main method, where you simulate the

building. You should instantiate a building, and several person instances. Then

you should simulate two different groups of people, arriving at different times,

and requesting to use the elevator. Print the state of the

building/elevator/people’s locations in order to show what is going on in the

building as the elevator runs. This is so the user can tell what is going on.

Implementation Details


The idea is that a client program should be able to create person instances and a

building instance. Then, each person could call a method to enter the building,

where the building instance is passed as a parameter. Then a method would be

called from the building instance on its elevator, creating a “job” or trip to be

executed. The details of each class and the necessary methods are below. Note

that you may use additional methods in your classes in order to have an

organized and modular solution. Analyze the code and decide how to implement

your solution. We are not looking for a uniquely right solution, so use your own

judgement as a programmer and describe your logic in a README.txt file.

Note: Feel free to pass as many parameters in each constructor method as you

see fit. Comment your code very well, as we will be evaluating your logic and

your understanding of object- oriented practices.

Building Class

public boolean enterElevator(Person person, int

floor) — This method will process the request made by a person to enter

the building. Then, it should pass on the request to an elevator instance.

Make sure that the elevator visits the first floor and then the floor requested

by the person.

person: the person that has requested access to the building

floor: the number of the desired floor


public void startElevator() — This will call a method in the

elevator instance that should process all current jobs.


public boolean enterFloor(Person person, int floor)

— This method should simply access the given floor object and call a

method to save a reference to the person in the given floor.

person: the person to access the floor

floor: the floor number to be entered ? ?


Person Class

public boolean enterBuilding(Building building, int

floor) — This method will simply call the appropriate method from the

building instance to enter the elevator and request a job.

building: the building to be entered

floor: the floor requested

public String getLocation() — You should hold a variable (that

you will need to update at certain moments) that will say the location of a

person. You can choose how to implement this, but you should return strings

like "In lobby”, "In Elevator", or "In floor 4", etc... ?


Floor Class

public boolean enterFloor(Person person) — This method

should save a reference to the person within the floor object

person: the person to enter the floor

Job Class

public Job(Person person, int floor) — This class is used

mostly to hold information.

person: the person that requested a job (or null if the elevator was

requested to go to the lobby to pick up a person)

floor: the floor number that has been requested

Elevator Class


public public boolean createJob(Person person, int

floor) — This method should simply add, in the right place, a new job to

be completed by the elevator.

person: the person that requested the elevator

floor: the desired floor number

public void cleanUpJobs() — This method will be used after

completing (and removing) a job. The use of this method should guarantee

that the jobs array is in a valid state.

public void processAllJobs() — This method should remove

jobs one by one (in the right order) and process them individually.

public boolean processJob(Job job) — This method should

process a job, and move the elevator floor by floor (while printing updates)

in order to reach the desired floor. Then, the exit method should be called,

simulating the exit of a person (if necessary).

job: the job to be processed

public boolean exit(Person person, int floor) — This

method should call a method on the building for a person to enter a given

floor (hold a reference to the person in the given floor).

person: the person exiting at a given floor

floor: the floor at which the person is exiting ?


Please make sure to read and understand the code provided before

attempting a solution. There are additional comments that are very

important to your task. If you draw a simple diagram of how the classes

interact and what the flow of the program will be before you start coding, it will

be much, much easier to complete this assignment.


Debugging

Use the debugger included with Eclipse to debug your program step by step:

1. Set a breakpoint in the code just before where you are experiencing a

problem. If you set the breakpoint on the 1st statement of your main

method, you will be able to step through every line of code in your

program.

a. Right click on the number of the line of code where you would like

to set the breakpoint

b. Select Toggle Breakpoint to set or remove


c. You will see a little blue dot appear to the left of the line number

when the breakpoint is set.




2. Run the program in Debug Mode

a. Click on the “Debugger” button


b. First time you run this, you will be prompted to switch perspectives.

Agree to that. Eclipse will open additional windows useful for the

debugging process


3. Set through your code to watch where each step takes. (1) You can jump

into the functions (all the way to the Java source code). (2) You can jump

over statements to execute them without going into them. (3) You jump

out of functions to get back to the calling function. (4) You can stop

execution to start again.


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