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Module 9 - Concurrency

Description

Concurrent programming is a paradigm that allows developers to write code that can execute in parallel (on multi-core systems) or with the illusion of parallelism (on single-core ones). Concurrent programming is very, very challenging and is ideally only used in support of well-defined and well-understood design problems, such as performing background operations or displaying animations. In fact, many typical concurrent programming problems already have a framework-based solution that hides the use of concurrency primitives. In this module, I will present the foundations of object-oriented concurrent programming and a few examples of the use of concurrency in practice.

Learning Objectives

After this module you should:

  • Understand the concept of a Thread and its usefulness for programming;
  • Be able to write basic concurrent programs in Java;
  • Understand the causes of basic concurrency errors including race conditions and deadlocks, and the mechanisms that help prevent them.
  • Be able to recognize when to and when not to use concurrency in application design;

Notes

Reading

Exercises

Exercises prefixed with ⭐ are optional, more challenging questions aimed to provide you with additional design and programming experience. For maximum learning effectiveness, I recommend peeking at the answers only after giving the problems an honest try.

  1. Write a program where one thread (NumberIncrementer) keeps adding to a shared data structure (make it a class NumberBox), and another thread (NumberPrinter) sleeps, periodically wakes up, and prints whatever number is in the box. Do you need to use synchronization? why or why not?
  2. Change the program of Exercise 2 so the number-incrementer threads only increments number every, say, 1 second, and the printer thread only obtains a number when a new one is available. Use conditions.
  3. Enhance the version developed for Exercise 2 so that a third (timer) thread interrupts both counter and printer threads after the number reaches 10.

Creative Commons License

Unless otherwise noted, the content of this repository is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.

Copyright Martin P. Robillard 2017