Understanding Java Concurrency And Multithreading

June 22, 2023
Understanding Java Concurrency and Multithreading

Every seasoned app developer and software engineer knows the importance of multithreading and concurrency in programming languages like Java, GO, and C++. In short, they help developers maximize their resources and get more done in less time. However, not everyone truly understands the science behind these concepts, and some don’t know how to use them properly.

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So, without further ado, let’s dive into Java concurrency and multithreading to understand how these features can save time and help you code like a pro.

Understanding Java Concurrency

Before we talk about Java concurrency or multithreading, it is a must to understand what the term means. Simply put, it is the ability to run multiple parts or programs in parallel or simultaneously. Besides minimizing the total time spent, the feature helps improve the program’s interactivity and throughput.

In addition, it is also essential to build familiarity with terms like processes and threads. The former runs independently and shares no link with other processes, and neither can access their shared data. In contrast, the latter also called a lightweight process, has access to other threads’ shared data present within the process.

That said, Java, by default, runs in a single process. However, you can integrate and work with multiple threads to enjoy concurrency in Java and unlock asynchronous behavior or parallel processing.

Why Use Concurrency or Multithreading?

Unlike before, when single-core systems had to go back and forth to multitask, modern-day systems rock multiple cores and have the hardware prowess to treat threads or processes individually, allowing users to utilize their CPU power to the fullest and take efficiency up a notch.

In short, concurrency in Java, or generally, helps increase throughput, better response, and speed up processing. However, everything works best in moderation, and multithreading has a limit also. So, only create as many threads as your CPU can house, and you can manage.

Important Concepts To Know

Context Switching

The technique enables sharing the CPU time across all running threads or processes.

Thread Pools

Thread pools enable the user to decouple task delivery and execution. The feature lets you reveal the executor’s configuration and switch executors on the go.

Home to homogenous threads or workers, a thread pool functions task-by-task. The workers take the task, execute, and return it back to the pool.


Locks, as the word suggests, limit access to a resource. For instance, Mutex is a lock used for mutual exclusion. It guards shared data and allows access to the resource one thread at a time.

Thread Safety

The concept enables different threads to access a single resource without triggering an error. Examples include a deadlock or a race condition.

Common Issues with Java Concurrency

Multithreading in Java is fun, but there is a chance you will run into trouble if you go overboard. Here are some issues associated with Java concurrency and working with multiple threads.


In multithreading, a deadlock occurs when a thread cannot access the required resources due to a clash with another. In this case, progress halts as both get tied up.

Race Conditions

Race conditions become an issue when two or more threads race through critical sections without synchronization. Here, the critical section implies any fragment of code with shared access.

In such cases, when a thread writes or reads a shared resource and executes it, the output changes, making the application data accessible to others inconsistent and outdated.


Besides deadlock, starvation is another ill of Java concurrency. Here, the thread never gets access to shared resources or CPU time.


Livelock implies when two threads get caught up in a repeated response loop, where both, attempting to break free, jam the progress. With triggered responses, they keep canceling out their actions and remain stuck.

How to Solve Java Concurrency Issues?

Evading Deadlock

There are two deadlocks common in concurrency in Java; nested and unnecessary locks. The first occurs when a user locks multiple threads, while the second occurs when they block threads unnecessarily. In practice, it is best to resist the urge to lock resources as they often end up deadlocking the system.

Avoiding Race Conditions

A simple yet often ignored trick to evade race conditions is thread synchronization, as the problem only surface when working with unsynchronized threads.

Resolving Starvation

In Java concurrency, using locks like Mutex or ReentrantLock is the surefire way to avoid starvation. Locks like these enforce a fair lock policy to ensure the thread first in the queue gets the nod.

Avoiding Livelock

Like starvation, Mutex or ReentrantLock also resolves livelock. Remember, it is best not to block locks unnecessarily and release previously locked-up resources upon completion.

The Wrap Up

Java concurrency and multithreading are incredible features to speed processes and up efficiency. However, it is best to use the functions smartly to avoid clogging up the system.

Also Read: A Guide To Assertions In Java

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