PV 168
Seminar 11
Agenda
- Project: Next Steps
- Project: Third Milestone
- Seminar task
- Seminar task reflection
● Fix all issues found during the Second Milestone review
○ Problems in the GUI (usability)
○ Code quality
● Cover your code with tests (to enable further refactoring)
○ Everything but GUI
● Make sure that all DB operations are performed out of Event Dispatcher
Thread
● Translate your application into two languages
○ English (as default)
○ Czech/Slovak/German/French/Russian/Filipino/Cebuano
Project: Next Steps
Project: Third Milestone
● Implement the fully functional application
○ In the scope agreed with the customer
● Deadline: 8. 1. 2021 23:59
○ The master branch of your repository at https://gitlab.fi.muni.cz contains complete application
● If you have any questions, ask assigned seminar tutor (the one who has
customer role for your project)
Seminar task
- You will be now split to teams consisting of four students
- Create and push the branch (see the next slides)
- Work on the tasks in the specified order (see the next slides)
- You have 60 minutes to solve all the tasks
- If you need any help, Ask for Help in Zoom
Working with branches in Git
● Clone the project https://gitlab.fi.muni.cz/pv168/employee-evidence
● Create new local branch
○ based on commit 81d72ee3 (current head of master branch)
○ with name week11-group0X-roomY (0X is seminar group, Y is breakout room number)
○ If you from group PV168/01 and breakout room 3, branch name is week11-group01-room3
● Pavel Hrdina or Petr Adámek will give you write access to employee-evidence
repository
○ Only one person per breakout room - the one who will use the computer for coding
○ Petr or Pavel will visit your breakout room to ask who is this person
○ In the meantime work on other tasks
● Push the branch to origin repository
1. Tasks #1 - #4 (Thread Quiz)
○ Look at the code, discuss it with your team partners and answer these questions
i. Is this code thread-safe?
ii. Is the scope of the synchronization appropriate?
○ If answer to any question above is no, explain why.
○ Write down your answers to /src/main/java/cz/muni/fi/pv168/threads/ThreadQuiz.txt
○ Commit your answers (one commit for all 4 tasks is sufficient)
2. Tasks #5 and #6 (Multi-thread Counter)
○ Commit each task separately!
3. Task #7 (Delete Operation in Background Thread)
○ Commit your solution
○ Don’t forget to push
Seminar task
Task #1: Thread Quiz 1
final class Counter {
private static int currentValue = 0;
public synchronized int next() {
return ++currentValue;
}
}
Task #2: Thread Quiz 2
final class Counter {
private static final Object LOCK = new Object();
private int currentValue = 0;
public int next() {
synchronized(LOCK) {
return ++currentValue;
}
}
}
Task #3: Thread Quiz 3
final class Counter {
private Integer currentValue = 0;
public int next() {
synchronized(currentValue) {
return ++currentValue;
}
}
}
Task #4: Thread Quiz 4
final class ThreadSafeContainer {
private final List<String> rows =
Collections.synchronizedList(new ArrayList<>());
public void addRow(String row) {
rows.add(row);
}
public synchronized void printRows() {
for (String row : rows) {
System.out.println(row);
}
}
}
Task #5: Multi-thread Counter
Fill in the implementation of Counter class to spawn 3 threads. These threads
cooperate on generating unique numbers from 0 to 50 and printing them on
standard output (not necessarily in the correct order) in the following format:
Thread 2: 1
Thread 3: 2
Thread 1: 0
Thread 2: 3
...
Thread 2: 47
Thread 3: 50
Task #6: Multi-thread Counter (in order)
● Commit the implementation of Task #5.
● Change the implementation to print all numbers in the correct order:
Thread 1: 0
Thread 2: 1
Thread 1: 2
Thread 3: 3
...
Thread 2: 49
Thread 3: 50
Task #7: Delete Operation in Background Thread
1. Modify the application not to call EmployeeDao.delete(...) in Event
Dispatcher Thread, but in some background thread.
2. Resolve the problems caused by concurrent execution of multiple delete
operations.
Link to slides
https://is.muni.cz/auth/el/fi/podzim2020/PV168/um/seminare/PV168-seminar-11.pdf
Conclusion
Any questions?