Skip to content

How one can Save you Concurrency Issues in Java content material and product suggestions are editorially unbiased. We would possibly generate income whilst you click on on hyperlinks to our companions. Learn More.

Java Programming tutorials

Concurrency is a elementary side of contemporary instrument construction, permitting systems to accomplish more than one duties concurrently. In Java, a multithreaded atmosphere permits programs to execute concurrent duties, but it surely additionally introduces the potential of concurrency issues. Those problems get up when more than one threads get entry to shared assets concurrently, resulting in race prerequisites, deadlocks, and information inconsistencies. On this programming educational, we can discover more than a few tactics and easiest practices to stop concurrency issues in Java.

Commonplace Concurrency Issues in Java

Concurrency issues in Java can get up from a number of not unusual resources. One widespread factor is race prerequisites, the place more than one threads try to adjust a shared useful resource concurrently, resulting in unpredictable results. This regularly happens when operations aren’t atomic or when synchronization mechanisms aren’t implemented the place wanted. Every other prevalent drawback is deadlocks, the place two or extra threads are looking forward to every different to free up assets, leading to a standstill. This may occur because of round dependencies or when threads gain locks in a special order. Moreover, inconsistent reads can happen when one thread reads a price in an inconsistent state because of every other thread’s changes. This may occur when correct synchronization isn’t in position. Listed below are some examples for example:

  1. Race Prerequisites: Those happen when two or extra threads try to adjust a shared useful resource at the same time as, resulting in unpredictable results.
    elegance Counter {
        non-public int depend = 0;
        public void increment() {
            depend++; // This operation isn't atomic
  2. Deadlocks: A impasse happens when two or extra threads are blocked indefinitely, every protecting a useful resource the opposite threads are looking forward to.
    elegance Useful resource {
        synchronized void method1(Useful resource different) {
            // Do one thing
        synchronized void method2(Useful resource different) {
            // Do one thing else
  3. Inconsistent Reads: This occurs when one thread reads a price this is in an inconsistent state because of every other thread’s changes.
    elegance SharedData {
        non-public int worth;
        public void setValue(int val) {
            this.worth = val;
        public int getValue() {
            go back this.worth;

You’ll be able to be told extra about thread deadlocks in our instructional: How to Prevent Thread Deadlock in Java.

Prevention Methods for Concurrency Problems in Java

Working out and addressing the above resources of concurrency issues is a very powerful for development tough and dependable multithreaded applications in Java. With that during thoughts, listed below are a couple of methods for fighting concurrency problems:

Use Thread-Protected Information Constructions

Java supplies an impressive concurrency framework via its java.util.concurrent bundle. This bundle gives high-level concurrency constructs akin to ExecutorThreadPool, and Lock interfaces, together with low-level synchronization mechanisms like synchronized blocks and risky variables. The java.util.concurrent bundle additionally comprises thread-safe information buildings akin to ConcurrentHashMapCopyOnWriteArrayList, and BlockingQueue. Those categories are designed to take care of concurrent get entry to with out further synchronization.

Right here is a few code that includes the ConcurrentMap elegance:

ConcurrentMap<String, Integer> concurrentMap = new ConcurrentHashMap<>();
concurrentMap.put("key", 1);
int worth = concurrentMap.get("key");

Synchronize Get admission to to Shared Sources

The synchronized key phrase means that you can create a synchronized block or approach to make certain that just one thread can get entry to the synchronized code block at a time.

elegance Counter {
    non-public int depend = 0;
    public synchronized void increment() {

Use Atomic Variables

The java.util.concurrent.atomic bundle supplies categories like AtomicIntegerAtomicLong, and AtomicReference that carry out operations atomically with out specific synchronization.

AtomicInteger atomicInt = new AtomicInteger(0);

Steer clear of Sharing Mutable Items

Every time imaginable, design your categories to be immutable, that means their state can’t be modified after introduction. This removes the desire for synchronization. Within the following code, the ImmutableClass can’t be changed as a result of it’s declared as ultimate:

public ultimate elegance ImmutableClass {
    non-public ultimate int worth;

    public ImmutableClass(int worth) {
        this.worth = worth;

    public int getValue() {
        go back worth;

Decrease Lock Rivalry

Lock competition happens when more than one threads compete for a similar lock. To reduce this, use fine-grained locking or tactics like lock striping.

elegance FineGrainedLocking {
    non-public ultimate Object lock1 = new Object();
    non-public ultimate Object lock2 = new Object();
    public void method1() {
        synchronized(lock1) {
            // Vital segment

    public void method2() {
        synchronized(lock2) {
            // Vital segment

Use risky for Variables Accessed by means of A couple of Threads

The risky key phrase guarantees {that a} variable’s worth is at all times learn from and written to the primary reminiscence, slightly than being cached in a thread’s native reminiscence.

elegance VolatileExample {
    non-public risky boolean flag = false;

    public void toggleFlag() {
        flag = !flag;

Practice Prime-Stage Concurrency Constructs

Make the most of categories from java.util.concurrent for higher-level concurrency control, akin to ExecutorSemaphoreCountDownLatch, and CyclicBarrier.

Right here’s a easy instance of the use of an Executor to execute a job:

import java.util.concurrent.Executor;
import java.util.concurrent.Executors;

public elegance Primary {
    public static void primary(String[] args) {
        // Create an Executor (on this case, a fixed-size thread pool with 5 threads)
        Executor executor = Executors.newFixedThreadPool(5);

        // Put up a job for execution
        executor.execute(() -> {
            Gadget.out.println("Activity performed!");

Ultimate Ideas on Combating Concurrency Issues in Java

Concurrency issues can also be complicated and difficult to debug. Via working out the foundations of concurrency and making use of the methods defined on this article, you’ll broaden Java programs which can be tough and loose from not unusual concurrency problems. Be mindful to make a choice the correct method to your explicit use case, bearing in mind components like the character of shared assets, efficiency necessities, and the choice of concurrent threads. Moreover, thorough trying out and code critiques are a very powerful to make sure the effectiveness of your concurrency prevention measures.

Learn: Best Practices for Multithreading in Java

Ready to get a best solution for your business?