The only guide you’ll need on concurrency & multithreading for senior engineers. Pressure test your skills with real-world practice problems from top companies.

Concurrency in Java is one of the most complex and advanced topics brought up during senior engineering interviews. Knowledge of concurrency and multithreading can put interviewees at a considerable advantage. This course lays the foundations of advanced concurrency and multithreading and explains concepts such as Monitors and Deferred Callbacks in depth. It also builds simple and complete solutions to popular concurrency problems that can be asked about in interviews like the Reader-Writer Problem and the Dining Philosopher Problem. While prior knowledge of concurrency is not required to follow through with this course, familiarity with the very basics of concurrency would be helpful.

Java Multithreading for Senior Engineering Interviews

As an example, we'll compare and contrast using a timer and a pool to schedule periodic or delayed threads.

# Timer
The achilles' heel of the <code class="clazz">Timer</code> class is its use of a single thread to execute submitted tasks. Timer has a single worker thread that attempts to execute all user submitted tasks. Issues with this approach are detailed below:
<ul>
<li>If a task misbehaves and never terminates, all other tasks would not be executed</li>
<li>If a task takes too long to execute, it can block timely execution of other tasks. Say two tasks are submitted and the first is scheduled to execute after 100ms and the second is scheduled to execute after 500ms. Now if the first task takes 5 minutes to execute then the second task would get delayed by 5 minutes rather than the intended 500ms.</li>
<li>In the above example, if the second task is scheduled to run periodically after every 500ms, then when it finally gets a chance to run after 5 minutes, it'll run for all the times it missed its turns, one after the other, without any delay between consecutive runs. </li>
</ul>

As an example, we'll compare and contrast using a timer and a pool to schedule periodic or delayed threads.

# Timer
The achilles' heel of the <code>Timer</code> class is its use of a single thread to execute submitted tasks. Timer has a single worker thread that attempts to execute all user submitted tasks. Issues with this approach are detailed below:
<ul>
<li>If a task misbehaves and never terminates, all other tasks would not be executed</li>
<li>If a task takes too long to execute, it can block timely execution of other tasks. Say two tasks are submitted and the first is scheduled to execute after 100ms and the second is scheduled to execute after 500ms. Now if the first task takes 5 minutes to execute then the second task would get delayed by 5 minutes rather than the intended 500ms.</li>
<li>In the above example, if the second task is scheduled to run periodically after every 500ms, then when it finally gets a chance to run after 5 minutes, it'll run for all the times it missed its turns, one after the other, without any delay between consecutive runs. </li>
</ul>

Contrasting Timer and ScheduledThreadPool

The Basics

Multithreading in Java

Java's Memory Model

Interview Practice Problems

Bonus Questions

Beyond the Interview

Java Concurrency Reference

Revision & Quizzes

An Example: Timer vs ScheduledThreadPool