Java Concurrency & Multithreading Complete Course

Practice for this video

Please check what happens if you:

1. Call the start method two times

2. Call the join method before the start method

3. Set the daemon flag after starting a thread

4. Call the join method for a daemon thread

Also, please read the documentation for class Runnable and methods

start, join and setDaemon of the class Thread

Practice for this video

Find the throughput of your system, for that:

1. Add some mathematical work to the method process instead of the Thread.sleep call

2. Add a global counter which will count, how many items were processed (it can be an atomic variable)

3. Find the optimal number of producer and consumer threads

4. Find the best throughput of your system

Practice for this video

Reimplement the merge-sort algorithm on your own using the CountDownLatch synchronization primitive

1. Create a queue for sorting tasks

2. Create a producer thread that publishes sorting tasks

3. Create consumer threads that take tasks from the queue and do sort

4. Create a method that waits for a competition of all sorting tasks and then does a merging stage

5. Add a test that checks that data are sorted correctly

Practice for this video

Implement your own capacity restricted queue:

1. With blocking methods put and take (it's not necessary to implement other methods) 

2. Replace with it the LinkedBlockingQueue in our example

3. Write a test that checks that your queue works correctly with several producers and consumers

You can use the synchronized keyword and wait/notify calls or ReentrantLock and Condition variable

Practice for this video

You have to make refactoring of code from the video and create a MapReduce framework. For that

1. Create a MapReduce class

2. Parameters of the constructor should be:

    text file (or path to the file)

    map function

    reduce function

3. Add a method execute

4. This method should return a collection of reduced Keys and Values

5. The type of Keys and Values should be generic. The Key can be Integer for example, and Value – Double.

6. Prepare a text file with several lines with numbers

7. Calculate the sum of values that are:

    less than 100 (first key)

    between 100-1000 (second key)

    greater than 1000 (third key)