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

# Introduction
<p>A system can achieve concurrency by employing one of the following multitasking models:</p>

<ul>
<li><p>Preemptive Multitasking</p></li>
<li><p>Cooperative Multitasking</p></li>
</ul>    
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# Preemptive Multitasking 
<p><span class="hi-yl">In preemptive multitasking, the operating system preempts a program to allow another waiting task to run on the CPU.</span> Programs or threads can't decide how long for or when they can use the CPU. The operating system’s scheduler decides which thread or program gets to use the CPU next and for how much time. Furthermore, scheduling of programs or threads on the CPU isn’t predictable. A thread or program once taken off of the CPU by the scheduler can't determine when it will get on the CPU next. As a consequence, if a malicious program initiates an infinite loop, it only hurts itself without affecting other programs or threads. Lastly, the programmer isn't burdened to decide when to give up control back to the CPU in code. </p>
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# Cooperative Multitasking 

<p><span class="hi-yl">Cooperative Multitasking involves well-behaved programs to voluntarily give up control back to the scheduler so that another program can run.</span> A program or thread may give up control after a period of time has expired or if it becomes idle or logically blocked. The operating system’s scheduler has no say in how long a program or thread runs for. A malicious program can bring the entire system to a halt by busy waiting or running an infinite loop and not giving up control. The process scheduler for an operating system implementing cooperative multitasking is called a cooperative scheduler. As the name implies, the participating programs or threads are required to cooperate to make the scheduling scheme work.</p>
</div>
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# Cooperative vs Preemptive
<p>Early versions of both Windows and Mac OS used cooperative multitasking. Later on preemptive multitasking was introduced in Windows NT 3.1 and in Mac OS X. However, preemptive multitasking has always been a core feature of Unix based systems.</p>
</div>
</div>


# Introduction
<p>A system can achieve concurrency by employing one of the following multitasking models:</p>

<ul>
<li><p>Preemptive Multitasking</p></li>
<li><p>Cooperative Multitasking</p></li>
</ul>    
</div>
</div>

# Preemptive Multitasking 
<p><span>In preemptive multitasking, the operating system preempts a program to allow another waiting task to run on the CPU.</span> Programs or threads can't decide how long for or when they can use the CPU. The operating system’s scheduler decides which thread or program gets to use the CPU next and for how much time. Furthermore, scheduling of programs or threads on the CPU isn’t predictable. A thread or program once taken off of the CPU by the scheduler can't determine when it will get on the CPU next. As a consequence, if a malicious program initiates an infinite loop, it only hurts itself without affecting other programs or threads. Lastly, the programmer isn't burdened to decide when to give up control back to the CPU in code. </p>
</div>
</div>

# Cooperative Multitasking 

<p><span>Cooperative Multitasking involves well-behaved programs to voluntarily give up control back to the scheduler so that another program can run.</span> A program or thread may give up control after a period of time has expired or if it becomes idle or logically blocked. The operating system’s scheduler has no say in how long a program or thread runs for. A malicious program can bring the entire system to a halt by busy waiting or running an infinite loop and not giving up control. The process scheduler for an operating system implementing cooperative multitasking is called a cooperative scheduler. As the name implies, the participating programs or threads are required to cooperate to make the scheduling scheme work.</p>
</div>
</div>


# Cooperative vs Preemptive
<p>Early versions of both Windows and Mac OS used cooperative multitasking. Later on preemptive multitasking was introduced in Windows NT 3.1 and in Mac OS X. However, preemptive multitasking has always been a core feature of Unix based systems.</p>
</div>
</div>


This lesson details the differences between the two common models of multitasking.

The Basics

Multithreading in Java

Java's Memory Model

Interview Practice Problems

Bonus Questions

Beyond the Interview

Java Concurrency Reference

Revision & Quizzes

Cooperative Multitasking vs Preemptive Multitasking