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


## Waking-up for no reason
    
<p>Spurious mean <b>fake</b> or <b>false</b>. A spurious wakeup means a thread is woken up even though no signal has been received. Spurious wakeups are a reality and are one of the reasons why the pattern for waiting on a condition variable happens in a while loop as discussed in earlier chapters. There are technical reasons beyond our current scope as to why spurious wakeups happen, but for the curious on POSIX based operating systems when a process is signaled, all its waiting threads are woken up. Below comment is a directly lifted from Java's documentation for the <code>wait(long timeout)</code> method.</p>
<b>

```java
* A thread can also wake up without being notified, interrupted, or
* timing out, a so-called <i>spurious wakeup</i>.  While this will rarely
* occur in practice, applications must guard against it by testing for
* the condition that should have caused the thread to be awakened and
* continuing to wait if the condition is not satisfied.  In other words,
* waits should always occur in loops, like this one:
* 
*     synchronized (obj) {
*         while (condition does not hold)
*             obj.wait(timeout);
*         ... // Perform action appropriate to condition
*     }
*
```
</b>
    </div>
</div>


# Waking-up for no reason
    
<p>Spurious mean <b>fake</b> or <b>false</b>. A spurious wakeup means a thread is woken up even though no signal has been received. Spurious wakeups are a reality and are one of the reasons why the pattern for waiting on a condition variable happens in a while loop as discussed in earlier chapters. There are technical reasons beyond our current scope as to why spurious wakeups happen, but for the curious on POSIX based operating systems when a process is signaled, all its waiting threads are woken up. Below comment is a directly lifted from Java's documentation for the <code>wait(long timeout)</code> method.</p>
<b>

```java
* A thread can also wake up without being notified, interrupted, or
* timing out, a so-called <i>spurious wakeup</i>.  While this will rarely
* occur in practice, applications must guard against it by testing for
* the condition that should have caused the thread to be awakened and
* continuing to wait if the condition is not satisfied.  In other words,
* waits should always occur in loops, like this one:
* 
*     synchronized (obj) {
*         while (condition does not hold)
*             obj.wait(timeout);
*         ... // Perform action appropriate to condition
*     }
*
```
</b>
    </div>
</div>

The Basics

Multithreading in Java

Java's Memory Model

Interview Practice Problems

Bonus Questions

Beyond the Interview

Java Concurrency Reference

Revision & Quizzes

Spurious Wakeups

Waking-up for no reason