Microsoft Word - project2.docx
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Title: “Project 2: An Application Employing Synchronized/Cooperating Multiple
Threads In Java Using Locks – A Banking Simulator”
Points: 100 points
Due Date: Sunday October 3, 2021 by 11:59 pm (WebCourses time)
Objectives: To practice programming cooperating, synchronized multiple threads of
execution.
Description: In this programming assignment you will simulate the deposits and
withdrawals made to a fictitious bank account (I’ll let you use my real bank account if
you promise to make only deposits! J). In this case the deposits and withdrawals will
e made by synchronized threads. Synchronization is required for two reasons – (1)
mutual exclusion (updates cannot be lost) and (2) because a withdrawal cannot occur
if the amount of the withdrawal request is greater than the cu
ent balance in the
account. This means that access to the account (the shared object) must be
synchronized. This application requires cooperation and communication amongst the
various threads (cooperating synchronized threads). (In other words, this problem is
similar to the produce
consumer problem where there is more than one producer and
more than one consumer process active simultaneously.) If a withdrawal thread
attempts to withdraw an amount greater than the cu
ent balance in the account – then
it must block itself and wait until a deposit has occu
ed before it can try again. As we
covered in the lecture notes, this will require that the depositor threads signal all waiting
withdrawal threads whenever a deposit is completed.
1. You should have six depositor threads and nine withdrawal threads
simultaneously executing. Use a FixedThreadPool() and an Executor object to
control the threads.
2. To keep things relatively simple, as well as to see immediate results from a series
of transactions (deposits and withdrawals), assume that deposits are made in
amounts ranging from $1 to $250 (whole dollars only) and withdrawals are made
in amounts ranging from $1 to $50 (again, whole dollars only). Since we have
more withdrawal threads than depositor threads, the account balance should
constantly decrease over time.
3. Once a depositor thread has executed, put it to sleep for few milliseconds
(randomly generate this number – don’t use a constant sleep time) or so (depends
CNT 4714 – Project 2 – Fall 2021
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a little bit on the speed of your system as to how long you will want to sleep the
depositor threads - basically we want to ensure a lot more withdrawals than
deposits) to allow other threads to execute. This is the only situation in which a
deposit thread will block.
4. For withdrawal threads, things will be a bit different depending on whether you
are working on a single or multi-core processor.
a. For single core processors, once a withdrawal thread has executed, have
it yield to another thread. Since the thread is giving up the processor
voluntarily, it will be unlikely to run again (attempt a second withdrawal
in a row), before another thread runs. Note however, that it does not
prevent it from running again, if all other withdrawal threads are blocked
and all depositors are sleeping, it will run again. So occasional back-to-
ack runs of withdrawal threads might occur.
. For multi-core processors, once a withdrawal thread has executed, have it
sleep for some random period of time (again, a few milliseconds should
e fine). Depending on which core a thread is executing, yielding the CPU
won’t ensure that the same thread will not run again immediately. While,
sleeping the thread will also not ensure that it will not run two or more
times in succession, it is less likely to do so in the multi-core environment.
c. What we don’t want to happen is a single withdrawal thread gaining the
CPU and then executing a long sequence of withdrawal operations. Recall
though that withdrawal threads block if they attempt to withdraw more
than the cu
ent balance in the account.
d. Similarly, we don’t want depositor threads monopolizing the CPU either
and causing the balance in the account to grow continuously. This would
most likely occur when the withdrawal threads are sleeping too long in
comparison to the average sleep time of the deposit threads. See page 7
for an illustration of this.
5. Assume all threads have the same priority. Do not give different priority to
depositor and withdrawal threads.
6. The output from your program must look reasonably similar to the sample output
shown below.
7. Do not put the threads into a counted loop for your simulation. In other
words, the run() method for all threads should be an infinite loop. Just stop
the simulation from your IDE after a few seconds.
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8. Do not use the Java synchronized statement. I want you to handle the locking
and signaling yourself. No monitors!
9. You must utilize a reentrant lock from the java.util.concu
ent.locks package for
implementing your locking protocols. We will specify no fairness policy for this
application. Do not create your own lock using a Boolean or any other type
of variable.
References:
Notes: Lecture Notes for Multithreaded Applications.
Restrictions:
Your source files shall begin with comments containing the following information:
* Name:
Course: CNT 4714 Fall 2021
Assignment title: Project 2 – Synchronized, Cooperating Threads Under Locking
Due Date: October 3, 2021
*/
Input Specification: Internal to the program.
Output Specification: Console based. Your output should appear reasonably similar
to the output shown below.
Deliverables:
(1) Zip up all of your .java files and submit them via WebCourses no later than
11:59pm Sunday October 3, 2021.
(2) Include at least one screen shot which illustrates the execution of your
synchronized threaded application. See below for some representative
examples. You can either do a screen shot of the console window like I did
elow or redirect your output to a file and take a screen shot from an editor.
Additional Information:
Shown below are three example screen shots of the output from this program to help
illustrate how your application is to operate and display the results. The last page
illustrates execution runs that you do not want to produce.
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Withdrawal thread W7
uns two times in a row.
This is ok. It may
happened from time to
time.
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All withdrawal threads are
locked. No withdrawal
thread can run until a
depositor thread runs.
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We don’t want to see this sort of scenario where the depositors are monopolizing the
account. Indication is the depositor threads aren’t sleeping long enough or the
withdrawal threads are sleeping too long.
Balance just continues to
grow and no blocking ever
occurs.
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