What is the difference between Java platform threads and virtual threads?

Platform threads map to operating-system threads, while virtual threads are lightweight JVM-managed threads designed to support large numbers of blocking tasks.

How do volatile and synchronized differ in Java concurrency?

volatile guarantees visibility of variable updates between threads, while synchronized provides both visibility and mutual exclusion for protected code.

How can Java deadlocks be prevented when using multiple locks?

Use a consistent lock acquisition order, keep lock scope short, and consider timed lock attempts with ReentrantLock.

Free Course Image Java Concurrency and Multithreading

Free online course Java Concurrency and Multithreading

Duration of the online course: 8 hours and 38 minutes

New

Build fast, reliable Java apps with a free concurrency course—master threads, virtual threads, locks, and ExecutorService with hands-on practice.

In this free course, learn about

Core concepts: concurrency vs parallelism; benefits of multithreading in modern CPUs
Creating, starting, and stopping threads; prefer Runnable/Callable to define thread work
Virtual threads: what they are and why they scale better than platform threads
Java Memory Model basics: heap role, visibility, ordering, and the happens-before guarantee
Using synchronized blocks/methods: mutual exclusion and visibility effects
volatile semantics: visibility guarantee, ordering constraints, and when it’s appropriate
CPU cache coherence and its impact on visibility/performance in concurrent Java code
ThreadLocal usage: per-thread state, retrieval behavior, and common use cases
Race conditions: how they happen and how to prevent them with proper synchronization
Thread pools and ExecutorService: task submission, lifecycle, and invokeAny behavior
Locks: ReentrantLock characteristics and when to choose it over synchronized
Deadlocks: common causes and simplest prevention technique (consistent lock ordering)
BlockingQueue and producer-consumer pattern: efficient coordination and CPU utilization
CAS/atomics, false sharing, signaling/wait-notify, ForkJoinPool, and ConcurrentHashMap

About the free online course

Modern Java applications rarely run in a quiet, single-threaded world. Web backends handle thousands of requests, data pipelines process streams continuously, and desktop or mobile apps must stay responsive while work happens in the background. This free online course helps you become confident with Java concurrency and multithreading so you can write software that is faster, safer, and easier to scale.

You will learn how threads actually behave in the JVM, how to create and manage them correctly, and when a different approach is a better fit. You will explore virtual threads and what they change for high-throughput, I/O-heavy services, then connect those ideas to the fundamentals that never go away: the Java Memory Model, visibility, ordering, and the happens-before guarantee. With that foundation, concepts like volatile, synchronized blocks, and CPU cache coherence stop feeling like magic and start becoming practical tools you can apply with intention.

As you move forward, the course strengthens your ability to design predictable multithreaded code. You will recognize and prevent race conditions, understand the difference between concurrency and parallelism, and choose strategies that match the problem instead of adding complexity. You will get comfortable with core building blocks used in real systems such as thread pools, locks like ReentrantLock, ThreadLocal, and higher-level execution patterns with ExecutorService, including methods that control how tasks are scheduled and results are retrieved.

You will also learn to spot classic failure modes early. Deadlocks, congestion, and false sharing can quietly destroy performance or reliability; here you will see why they happen and how to avoid them through disciplined structure and simple prevention techniques. The course connects these ideas to scalable coordination patterns like producer-consumer with BlockingQueue, signaling between threads, and efficient parallel execution using ForkJoinPool. By the end, you will be better prepared to reason about concurrency tradeoffs and build Java applications that remain correct under load.

Course content

Video class: Java Concurrency and Multithreading - Introduction 14m
Exercise: What is a primary advantage of multi-threading in modern computing?
Video class: Java Threads - Creating, starting and stopping threads in Java 17m
Exercise: Which method is recommended to define the code a thread should run in Java?
Video class: Java Virtual Threads 09m
Exercise: What is a primary advantage of virtual threads in Java over platform threads?

Video class: The Java Memory Model - The Basics 23m
Exercise: What is the main role of the heap in Java memory management with threads?
Video class: Java Happens Before Guarantee - Java Memory Model - Part 2 26m
Exercise: What role does the Java 'volatile' keyword play in multithreaded applications?
Video class: Java Synchronized - The synchronized keyword in Java and Java synchronized blocks and methods 45m
Exercise: What is the effect of a synchronized method in Java?

Video class: Java Volatile 21m
Exercise: What is the purpose of the 'volatile' keyword in Java?
Video class: CPU Cache Coherence Java Concurrency 05m
Exercise: What is Java's thread visibility guarantee related to volatile variables?
Video class: Java ThreadLocal 14m
Exercise: What value does a thread retrieve from a Java ThreadLocal instance it set earlier?

Video class: Race Conditions in Java Multithreading 22m
Exercise: What is a race condition in multithreading?
Video class: Concurrency vs Parallelism 09m
Exercise: What is the difference between concurrency and parallelism?
Video class: Thread Pools in Java 18m
Exercise: How does a thread pool manage task execution?

Video class: Java Lock 28m
Exercise: What is a key characteristic of the ReentrantLock class in Java?
Video class: Java ExecutorService - Part 1 20m
Exercise: What is the purpose of the invokeAny method in Java Executor Service?
Video class: Java ExecutorService - Part 2 21m

Video class: Java ExecutorService Using Virtual Threads 04m
Exercise: What is a key benefit of using an Executor service with virtual threads in Java 19?
Video class: Deadlock in Java 17m
Exercise: What can lead to a deadlock in a multithreading environment?
Video class: Deadlock Prevention in Java 17m
Exercise: What is the simplest deadlock prevention technique discussed?

Video class: Java BlockingQueue 17m
Exercise: What is a key feature of a Java Blocking Queue?
Video class: Producer Consumer Pattern - With Java Example 19m
Exercise: What is an efficient way to utilize CPU resources in the producer-consumer pattern?
Video class: Compare and Swap in Java 24m
Exercise: What does the 'compare and swap' functionality do in a concurrent algorithm?

Video class: False Sharing in Java 17m
Exercise: What is False Sharing in Java?
Video class: Single-threaded and Same-threaded designs 18m
Exercise: What is the advantage of a single-threaded design in server architecture?
Video class: Thread Congestion in Java 17m
Exercise: How can thread congestion be alleviated in a Java concurrency setup?

Video class: Thread Signaling in Java 23m
Exercise: How does thread signaling work in Java?
Video class: Java ForkJoinPool 27m
Exercise: What is a key feature of Java Fork Join Pool?
Video class: Java ConcurrentMap and ConcurrentHashMap 14m
Exercise: Which Java map implementation offers the best concurrency?

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