1. Slide design: Dr. Mark L. Hornick
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6/4/2018
Week 3, Day 1: Threads
Muddiest Point
Balancing load
Transferring tasks to the Event Dispatch Thread
Transferring tasks between threads manually?
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Slide design: Dr. Mark L. Hornick
Content: Dr. Hornick
Errors: Dr. Yoder
Dr. Yoder

2. Questions on Lab? I've received some good ones by email SE-2811
Dr. Mark L. Hornick

3. Threading Muddiest Point
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6/4/2018
Threading Muddiest Point
Notify() Is it always the same thread until it has nothing to do?
notify() who?
Why do the threads jump out of order in your example program? Why doesn't it go thread 1 then 2 then 3?
Is there a way to even the load so all 3 threads finish at the same time?
even loading?
More thread examples
more examples
Nothing
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Dr. Mark L. Hornick
Dr. Yoder

4. Threading Muddiest Point
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6/4/2018
Threading Muddiest Point
Everything seemed pretty straightforward today
Will we learn about more ways to use threads?
more examples
What is synchronizing "best practice"?
best practice
None.
How do all three threads know that they can leave the method if another thread doesn't come through and notify() them?
leaving the method
In what other ways can multi threading be used for?
Have a great weekend!
hope you did too!
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Dr. Mark L. Hornick
Dr. Yoder

5. Synchronizing Best Practice
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6/4/2018
Synchronizing Best Practice
Unless you KNOW that code will be used multi-threaded, don't synchronize it
(Vector vs ArrayList)
If a variable will be accessed by multiple threads, synchronize every access to that variable
If one thread must wait on another thread's result, synchronize that thread.
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Dr. Mark L. Hornick
Dr. Yoder

6. Wait and Notify… wait() --- stop here until notified
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6/4/2018
Wait and Notify…
wait() --- stop here until notified
notify() --- notify a waiting thread that it can continue
notifyAll() – wakes up all waiting threads
Like most threading methods notify() does not guarantee that any given thread will start next.
Details:
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Dr. Mark L. Hornick
Dr. Yoder

7. Multi-threading in Swing
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6/4/2018
Multi-threading in Swing
The Single-Thread Rule
Once a Swing component has been realized, all code that might affect or depend on the state of that component should be executed in the event-dispatching thread.
-- Sun Tutorial “Threads in Swing,”
Way Back Machine
What events should be handled by the event dispatching thread?
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Dr. Mark L. Hornick
Dr. Yoder

8. Multi-threading in Swing
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6/4/2018
Multi-threading in Swing
“A Swing component that's a top-level window is realized by having one of these methods invoked on it:
setVisible(true)
show() /** Deprecated */
pack()
From the “Obsolete” Java Swing Tutorial
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Dr. Mark L. Hornick
Dr. Yoder

9. Lambda Expression Syntax
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6/4/2018
Lambda Expression Syntax
Exercise: What parts does a regular method have?
Lambda Expression: A variety of syntaxes are available:
<arguments> -> <method body>
(Scanner in) -> {int x = in.nextInt(); return x+1;}
(int x) -> x+1
() -> System.out.println(“hi”)
x -> x+1
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Dr. Mark L. Hornick
Dr. Josiah Yoder

10. SE-2811
6/4/2018
I have been programming C# for 10 months now. I am now learning multi-threading and seems to be working nicely. I have multi-dimension array like
string[,] test = new string[5, 13];
I have the threads calling methods that end up saving their outputs to different coordinates inside the array above, without any one thread writing to the same location as another thread.
So thread1 might write to test[1,10] but no other thread will ever write to test[1,10]
My question is: I have read about using locks on objects like my array, do I have to worry at all about locks even though my threads might access to the test array at the same time but never write to the same coordinates(memory location)?
So far in my testing I have not had any issues, but if someone more seasoned than myself knows I could have issue then I'll look into use locks.
To best answer this question requires advanced knowledge of writing lock-free code. That will have to wait for another class…
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Dr. Mark L. Hornick
Dr. Yoder

11. What would you answer? string[,] test = new string[5, 13];
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What would you answer?
string[,] test = new string[5, 13];
thread1 might write to test[1,10] but no other thread will ever write to test[1,10]
do I have to worry at all about locks?
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Dr. Mark L. Hornick
Dr. Yoder

12. https://www.polleverywhere.com/free_text_polls/zIp2tH2IVWjXv4H SE-2811
6/4/2018
Muddiest Point
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Dr. Mark L. Hornick
Dr. Yoder