The Elevator Problem
You have been hired by
the university to build a controller for an elevator in the 10 storied
administration building. The elevator is represented as a thread. Each
person boarding or leaving the elevator is also represented by a thread.
You would need to implement the methods called by the arriving person.
e.g. a method ArrivingGoingFromTo(int atFloor,
int toFloor) should wake up the elevator (if necessary) and tell
it which floor to go to. The elevator is fast but it is not instantaneous,
it takes only 100 ticks to go from one floor to the adjacent one. For simplicity,
you can assume the following:
There is only one elevator and it holds 10 people of arbitary weight.
The elevator 'knows' the details (ID, arrival floor, destination floor
etc) of the people when they enter.
There is only one person entering the elevator at a floor at a time.
The elevator ascends one floor at a time without skipping floors.
When not in service, the elevator waits at the last floor it visited and
You have to come up with
a way of storing the requests to the elevator e.g. if a person is accessing
the elevator at the 3rd
floor and some body is trying to get
access from the 5th
floor then latter person has to wait before
he could place his request. In other words (s)he has to be put in a queue.
Also if the elevator is going upwards all the requests for the destinations
downwards should not be accepted until it starts its downward motion and
These specifications are for the "vanilla option" of the implementation.
Any form of creativity that you feel like putting in that will add interest
to my marking of the project (GUIs, multiple elevators, 'smart' elevators
etc) is encouraged. The marks awarded for the project will reflect
The assignment has
to be done in Java.
The program will have
two major classes “elevator” and “person” both of which will extend the
Java thread class (or extend runnable
interface). Each "person" should be generated with a random arrival
time, arrival floor and destination floor and have a unique ID for identification
In order to simulate the
100 ticks between the two consecutive floors, you can use the “wait
(100)” construct. You can refer to the website http://java.sun.com/docs/books/tutorial/essential/threads/waitAndNotify.html
for details of how to use “wait” for this purpose.
You can assume 100 ticks
is equivalent to your 1 unit of time (discussed above).
In order to compile a java
code, you first have to run the java compiler with “javac <filename>“
and after it gets compiled execute it with “java <filename(executable)>”.
Command line parameters
The format for the output
file should be something like following.
“Person (Thread ID)
# makes request at time # starting at floor # with the destination floor
There should be as many
lines printed as are the number of requests. You should also generate
an output file output.dat to
store your output.
Note: You must assume
that you the starting time for the first request is 0.
Deliverables and instructions for submission:
Please also write a short (5 page max) design documentation which may get
you some partial credit if your program does not execute.
You have to turn in all you source files, documentation and also all the
generated class files for the unix platform.
Mail the above to me with a statement that you have done it yourself except
the parts where otherwise stated and that you are aware of the University
rules concerning plagiarism at http://www.compapp.dcu.ie/current/policy/plagiarism.htm
Deadline for submission is the last friday of semester eg Friday
19th of December at 5.00pm. This is a hard deadline and
marks will be docked at the rate of 10% per day for latecomers.