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What is Java Concurrency?

What is Java Concurrency?

This post will explain What is Java Concurrency. The capacity of the Java platform to conduct many processes concurrently is known as Java Concurrency. Several Java programmes or sections of a single Java programme could be used for the operations. Processes and threads are two crucial elements that Java Concurrency depends on. Threads are one of the two components that are important. You can improve the performance of processors by using Java Concurrency or many threads.

What is Java Concurrency?

In this article, you can know about What is Java Concurrency? here are the details below;

Java allows you to run numerous programmes simultaneously on a single multi-core CPU, eliminating the need for additional processors. Recognize that a multi-core processor will have numerous cores packed into a single CPU. Many programmes or portions of a programme can run simultaneously on all of these numerous cores. To help you understand more about Java concurrency, we’ve created this tutorial.

You will quickly learn about processes & threads, thread objects, Java Concurrency models, synchronisation, liveliness, immutable objects, and high-level concurrency in the following sections. Let’s start with the subjects.

What is Concurrency software?

Concurrency software is any programme that can perform numerous tasks at once.

In other words, the software enables parallel execution of a large number of programmes or portions of a single programme.

If you wish to connect the idea of concurrency software with a practical application, think about a word processor.

A word processor can format text, reply to mouse and keyboard input, and print documents concurrently.

The ability of audio applications to read digital audio from networks, play it back, decompress it, and update the display — significantly all at once — is another example of concurrency.

What is Java Concurrency?

One of the multiple widely used programming languages is, as you are aware, Java.

It has Java class libraries and high-level concurrency Interfaces that facilitate concurrency.

Concurrent programming in Java is implemented using the package Java.util.concurrent.

This package includes classes with practical functionalities, standardised, compact, and extensible frameworks, and many other things.

Packages like Java.util.concurrent.locks and Java.util.concurrent.atomic packages are also included with Java.util.concurrent.atomic.

Threads can be used to run lengthy and intricate Java programmes thanks to these frameworks, packages, and classes.

Alternatively, you can run many apps simultaneously.

Running a programme utilising Java Concurrency can dramatically reduce processing time and enhance throughput.

What are Processes and Threads?

The two key components of Java concurrency are processes and threads.

They primarily assist with the development of a sophisticated Java execution environment.

It resembles a closed habitat in several ways.

Let’s examine them in more detail below:

Processes: A process is nothing more than a complete and private set of runtime resources.

Each process has its own memory.

Processes in a system can communicate with one another using pipes and sockets.

They also promote communication between various systems.

Remember that pipes and sockets are examples of inter-process communication elements.

What are Threads objects?

They function within a process and are the foundation of Java Concurrency.

There will be at least one thread in each process.

A thread can be thought of as a kind of virtual CPU on which Java programmes can be executed.

An programme can execute many threads simultaneously.

Threads often follow the priority.

Hence, the thread with the highest priority is executed first.

Recognize that processes and threads both consume the same resources.

The resources could be anything, including RAM or open files.

In addition, creating a thread uses fewer resources than creating a process.

What are the different java Concurrency Models?

Recognize that each thread is linked to a Thread class object.

Using thread objects, Java Concurrency provides two approaches for concurrency creation in programmes.

When the application needs to start an asynchronous job, you must instantiate the Thread class if you wish to directly handle thread creation and management.

Similar to this, you must transfer the duties of the application to executors if you want to separate thread creation and management from the rest of the application.

The following section will go through how to use thread objects:

Programs have the ability to establish Thread instances and execute Thread-specific instructions.

It is accomplished using a subclass Thread and a Runnable object, respectively.

The Thread.sleep object is utilised when pausing threads to put the current thread’s execution on hold for a specified amount of time.

Other threads are permitted to use processors during this pause.

During this pause, other programmes may also utilise the CPUs.

Breaks and Joins:

To halt thread operations and assign them to carry out different tasks, you can use interrupts in Java Concurrency.

An interrupt flag is enabled to transmit the interrupt status when an interrupt is applied.

The flag is set in this instance using the Thread.interrupt object.

It is necessary to call the static method Thread.interrupted to remove the flag status.

Similar to this, one thread can inquire about the interrupt status of another thread using the non-static method isInterrupted.

In addition, you can use the join technique to make one thread wait for another until it finishes its task.

Which Concurrency Models Are Available in Java?

The various channels of communication that might occur between threads are essentially described by concurrency models.

In Java concurrency, there are three fundamental models that are used:

1. Parallel Workers Model

The primary programme in this paradigm is broken up into numerous subprograms.

These subprograms will execute concurrently over various model threads or workers.

Each worker or thread in this instance will carry out a distinct task.

The key characteristic of this approach is that it forbids any worker or thread from being idle.

In other words, each thread or worker will execute a certain section of a programme.

2. Assembly Line Model

This approach is sometimes referred to as an Event-driven or Reactive model.

Tasks can be distributed among the assembly line’s several threads in this manner.

On an assembly line, each worker or thread will perform a different task while moving progressively in the same direction.

A task is sent to the next thread once it has been finished by the previous thread.

Recognize that this paradigm makes use of non-blocking I/O.

According to this concept, the CPU doesn’t waste time doing the I/O operation.

Keep in mind that to run a whole programme, you need to employ numerous assembly lines.

3. Functional Parallelism

To conduct numerous tasks concurrently, this paradigm makes advantage of multiple CPUs.

Function calls are used to achieve it.

Every function call in this case is independent.

It implies that function calls are carried out by different CPUs.

What is Synchronization In Java Concurrency?

Typically, threads communicate by exchanging access to fields and the data those object reference fields refer to.

Yet, it causes two different kinds of errors: thread interference and memory consistency.

The tool that aids in overcoming these problems is synchronisation.

Let’s first talk about thread interference and memory consistency problems.

Thread Interference: It is important to highlight that interleaving is the cause of this problem, which is a straightforward observation.

It signifies that the same data is being acted upon by two processes in two distinct threads.

In other words, an issue happens when steps in two threads cross over.

Memory Consistency Error: This error happens when threads have divergent ideas of what constitutes the “same data,” as the name implies.

In actuality, this issue has several different root causes.

And by comprehending the “happens-before” relationship, this error can be avoided.

This connection guarantees that memory writes performed by one statement are visible to another.

Recognize that one of the behaviours that establishes “happens-before” relationships is synchronisation.

It is used to get around memory consistency issues because of this.

Read the following if you’re interested in learning how to avoid these mistakes.

Here, we’ll look into synchronised methods and how they avoid the aforementioned mistakes.

Synchronized methods help prevent thread interference and memory inconsistency errors in Java Concurrency.

You can make an object visible to many threads by performing reads and writes on its variables using synchronised methods.

You can successfully avoid the aforementioned mistakes as a result.

Atomic access is one of the essential components of synchronisation.

Now, let’s define atomic access.

Atomic action in Java Concurrency happens completely or not at all.

Atomic action doesn’t have any side effects till it’s finished.

For example, except for long and double variables, reads and writes are atomic operations for reference and primitive variables.

For all explosive variables, including long & double variables, reads and writes are atomic operations.

What is Liveness in Java Concurrency?

Liveness is essentially the capacity of concurrent programmes to execute threads on time, free of delays and locks.

In Java Concurrency, it is not always achievable, though.

Thread contention occurs when multiple threads attempt to access the same resource.

The Java runtime delays or pauses the execution of some threads as a result.

Be aware that thread contention takes the form of starvation and livelock.

Let’s take a quick look at them below:

Deadlock: It occurs when two or more threads are continuously blocked.

They won’t carry on operating after that.

This is due to the threads’ constant waiting.

Livelock and starvation do not result in the same catastrophic problems as a deadlock.

To continue running the application, these must be swiftly fixed.

Starvation occurs when threads are unable to access shared resources.

They are therefore unable to advance farther.

This is a result of resource-hogging threads that use common resources continuously.

As a result, during Starvation, the shared resources won’t be accessible to other threads.

Livelock, another type of thread contention, is the undesirable scenario that develops when threads react to one another’s actions at the same time.

In a livelock situation, threads are not entirely blocked, but they will be occupied responding to each other’s actions.

What are immutable objects in java Concurrency?

Once created, immutable objects cannot change their state.

They are immune to thread interference thanks to this property.

And they never change to an inconsistent condition.

The issue at hand is how to maintain immutable objects’ original state at all times.

The solution is provided below.

To define immutable objects in Java concurrency, you can use a few different techniques.

Here are several examples:

The techniques that could alter object fields shouldn’t be used.

Making all object fields private and final would be beneficial.

You shouldn’t permit mutable objects to alter while instance fields have references to them.

What are High-level Concurrency objects?

We can efficiently operate a large number of concurrent apps by employing high-level building components.

As a result, we may utilise multiprocessor and multi-core systems to their full potential.

Let’s look at a few high-level concurrency objects below:

1. Lock objects

Be aware that a lock object can only be used by one thread at a time.

With the assistance of their condition objects, lock objects support the wait or notify mechanism.

Lock objects are fantastic because they can reverse attempts to open a lock.

When the lock is not immediately accessible, the tryLock function fails.

The lockInterruptibly function behaves similarly, backing out if the lock is acquired before an interrupt is sent by another thread.

2. Executors

To improve speed, it is always preferable to segregate “thread generation and thread management” from the rest of the application.

In running complex programmes, this method must be used.

Executors are objects that contain the necessary functions to carry out this strategy.

Concurrency Objects at the High Level

Executors define high-level APIs for starting and managing threads in Java Concurrency.

Thread pools, executor interfaces, and Fork/Join are their three key parts.

Executor interfaces initially offer three executor object types: executor, executor service, and scheduledexecutorservice.

Next, thread pools are collections of worker threads used to carry out a variety of tasks.

They reduce potential extra costs associated with establishing threads.

Due to their large memory footprint, thread objects incur overhead.

The third one, Fork Join, exists a framework that nables efficient use of numerous CPUs.

All processors are used in this framework, which divides jobs into manageable chunks.

Because of this, Java Concurrency significantly improves the processing performance of processors.

3. Concurrent Collections

Another high-level concurrency object of Java Concurrency is Concurrent Collections.

They assist in effectively managing massive amounts of data, which lessens the requirement for synchronisation.

4. Atomic Variables

They prevent memory inconsistency issues and lessen the need for synchronisation in Java concurrency.

Classes that make it easier to perform atomic actions on single variables can be found in the Java.util.concurrent.atomic package.

Get High-Paying Jobs by Learning Java Concurrency Interview Questions and Answers

How to Define and Start a Thread in Java Concurrency?

In general, applications can easily generate new thread instances, but they must also supply the code that will run on the threads.

Java Concurrency offers two ways to accomplish it:

supplying a Runnable object.

Using a Thread of a Subclass.

Method 1: Providing Runnable Object

The run method is offered by the runnable interface.

The thread’s code is contained in this procedure.

The runnable objects are then transferred to the thread function Object() { [native code] }.

This Java Concurrency notion is illustrated below with an example.

Including a Runnable Object

Method 2: Using a Subclass Thread

Even if the run method is inactive, the thread class can still implement Runnable.

An application will subclass thread in this situation.

Moreover, it offers its own run method implementation.

This Java Concurrency concept can be explained using the example below.

How to Pause Execution with sleep in java concurrency?

Thread.Sleep in Java Concurrency allows you to temporarily halt a thread’s operation for a set amount of time.

You can do this to make the CPUs accessible to other threads and programmes.

There are two different sleep implementations available in Java.

One version defines the sleep time in milliseconds, whereas another specifies it in nanoseconds.

Keep in mind that interrupts can be sent to end sleep periods.

The example below demonstrates how to use sleep to print messages at four-second intervals.

How to use Atomic variables in java concurrency?

How to kill threads in java concurrency?

In Java, threads can be terminated in one of two methods. Flags and interruptions can be used to do this. Using Flags: A flag is used to indicate whether a thread is active or not. Depending on the situation, you can utilise this flag to take corrective action. You can use flags to kill a thread by using the code that follows.

By setting the Running variable to false in this case, you can influence how things are carried out. AtomicBoolean can also be used for concurrency. Java Concurrency: Terminate Threads Using Flags Using Interrupts: Flag-based codes typically have some shortcomings. When there are numerous strands, things will become complicated. You can use the interrupted flag instead of the Boolean flag. Using Interrupts to Terminate Threads in Java Concurrency


Java Concurrency improves execution performance and reduces processing time, as you may have guessed. We also hope that this course taught you everything there is to know about Java concurrency.

Keep in mind that Java Concurrency taught you about processes and threads, thread objects, concurrency models, and much more. You must now have a greater level of trust in the topic after having first-hand experience defining, initiating, stopping, and killing threads.

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