A thread is used to perform parallel execution in Java e.g. while rendering screen your program is also downloading the data from the internet in the background. There are two types of threads in Java, user thread and daemon thread, both of which can use to implement parallel processing in Java depending upon the priority and importance of the task. The main difference between a user thread and a daemon thread is that your Java program will not finish execution until one of the user threads is live. JVM will wait for all active user threads to finish their execution before it shutdown itself.
How to join two threads in Java? Thread.join() example
You can join two threads in Java by using the join() method from java.lang.Thread class. Why do you join threads? because you want one thread to wait for another before starts processing. It's like a relay race where the second runner waits until the first runner comes and hands over the flag to him. Remember, unlike sleep(), join() is not a static method so you need an object of java.lang.Thread class to call this method. Now, who calls and who wants, and which thread dies? for example, if you have two threads in your program main thread and the T1 which you have created.
How to stop a thread in Java? Example
Today we're going to learn about how to stop a thread in Java. It's easy to start a thread in Java because you have a start() method but it's difficult to stop the thread because there is no working stop() method. Well, there was a stop() method in Thread class, when Java was first released but that was deprecated later. In today's Java version, You can stop a thread by using a boolean volatile variable. If you remember, threads in Java start execution from the run() method and stop, when it comes out of the run() method, either normally or due to any exception. You can leverage this property to stop the thread.
10 Things about Threads Every Java Programmer Should Know
Thread in Java is one of those topics which always confuse beginners but given the importance and strength it provides to the Java language, it's very important for every Java developer to learn and understand the fundamental concept of multi-threading and basic points about Thread in Java. I had started thread programming in Java by animating a couple of words in Applets, that was an amazing experience to code animation, but after spending almost 10 years on developing core Java applications and I am still discovering things about threading and concurrency. My first program which involves Thread had three words dropping from each corner of the screen and I was excited to see that animation driven by Java thread.
What is Thread and Runnable in Java? Example
What is Thread in Java?
Thread in Java is an independent path of execution that is used to run two tasks in parallel. When two threads run in parallel that is called multithreading in Java. Java is multithreaded from the start and has excellent support of Thread at language level e.g. java.lang.Thread class, synchronized keyword, volatile and final keyword make writing concurrent programs easier in Java than any other programming language like C++. Being multi-threaded is also a reason for Java's popularity and being the number one programming language.
Top 10 Udemy Courses to Learn Java Multithreading and Concurrency in 2025 - Best of Lot [UPDATED]
Hello guys, if you want to learn multithreading and concurrency in Java and
looking for the best learning material like books, tutorials, and online courses
then you have come to the right place. Earlier, I have shared the
best Core Java courses
and
best data structure and algorithm courses
and in this article, I am going to share the best online courses to learn
Multithreading in Java. These courses are curated from the best online learning
websites like Udemy, Pluralsight, and Coursera and will teach you Java
Multithreading from scratch. But, before we get to the best courses that you can
use to learn more about multithreading in Java, let me tell you what
multithreading exactly is.
Top 12 Java Thread, Concurrency, and Multithreading Interview Questions Answers
Hello guys, Multithreading is an important feature of the Java programming language, which
means threads are also an important part of any Java interview. It's true and
in fact, at beginners and freshers, level
Thread interview questions in Java
are one of the most difficult to answer. One reason for interview questions
related to multithreading and concurrency being difficult is confusion around
how multiple threads work together and the second is threads are genuinely a
complicated topic to understand and use correctly.
How to use fixed size thread pool Executor in Java? Example Tutorial
We are again with new article that is on using fixed size thread pool executor in Java. The main aim of this article is to give you idea about how to declare string in java and about different ways of declaring. So our viewer will have great knowledge after reading this. If you don't know, a FixedSizeThreadPool is a type of Java Executor that uses a fixed number of threads to carry out tasks. When you have a small number of tasks to complete and want to manage the number of threads that can be used to complete those tasks, this kind of executor is helpful.
Difference between ReentrantLock vs synchronized lock in Java? Example Tutorial
In concurrent programming, synchronization is essential to ensure that multiple threads can safely access shared resources without causing data inconsistencies or race conditions. In Java, there are two primary mechanisms for achieving synchronization: ReentrantLock and the synchronized keyword. The ReentrantLock and synchronized lock both serve the purpose of allowing exclusive access to critical sections of code, but they differ in terms of flexibility, performance, and the level of control they provide to developers. Understanding the nuances between these two synchronization approaches is crucial for Java developers aiming to build efficient and reliable concurrent applications.
Difference between Fixed and Cached Thread pool in Java Executor Famework
There are mainly two types of thread pools provided by Javas' Executor framework, one is fixed thread pool, which starts with fixed number of threads and other is cached thread pool which creates more threads if initial number of thread is not able to do the job. The newCachedThreadPool() method is used to create a cached pool, while newFixedThreadPool() is used to construct a thread of fixed size. Cached thread pool executes each task as soon as they are submitted, using an existing thread if its idle or creating new threads otherwise, while in case of fixed thread pool, if more tasks are submitted then idle threads then those task are put into a queue and later executed once any other task has finished.
What is Synchronized Keyword and Method in Java? Example
synchronized keyword in Java is one of the two important keywords related to concurrent programming in Java, the other being a volatile keyword. the synchronized keyword is used to provide mutual exclusion, thread safety, and synchronization in Java. Unlike Volatile keyword, synchronized keyword is not an application to instance variable and you can only use synchronized keyword either with synchronized method or block. synchronized keyword work with the concept of lock, any thread which holds a lock on which synchronized method or block is locked, can enter otherwise thread will wait till it acquires the lock. In Java programming language every object holds a lock and every class holds a lock, like two String objects s1, s2 holds two different object lock,s and String.class is used to represent class lock.
Difference between wait() and join() methods in Java Multithreading? [Answered]
Hello guys, if you are wondering what is difference between wait() and join method in Java multithreading and when to use each of them then you have come to the right place. Earlier, I have shared best Java multithreading courses and books and today I will answer this common Java threading question for you. Even though both wait() and join() methods are used to pause the current thread and have a lot of similarities they have different purposes. One of the most obvious differences between the wait() and join() methods is that the former is declared in java.lang.Object class while join() is declared in java.lang.Thread class. This means that wait() is related to the monitor lock which is held by each instance of an object and the join method is related to the thread itself. The wait() method is used in conjunction with notify() and notifyAll() method for inter-thread communication, but join() is used in Java multi-threading to wait until one thread finishes its execution.
Difference between Callable and Runnable in Java? call() vs run() method
Hello guys, the difference between the Callable and Runnable interface in Java is one of the interesting questions from my list of Top 15 Java multi-threading questions, and it’s also very popular in various Java Interviews. The Callable interface is newer than the Runnable interface and was added on Java 5 release along with other major changes e.g. Generics, Enum, Static imports, and variable argument method. Though both Callable and Runnable interfaces are designed to represent a task, which can be executed by any thread, there is some significant difference between them.
What is Volatile Variable in Java? When to Use it? Example
What is a Volatile variable in Java?
The volatile variable in Java is a special variable that is used to signal threads and compilers and runtime optimizers like JIT that the value of this particular variable is going to be updated by multiple threads inside the Java application. By making a variable volatile using the volatile keyword in Java, the application programmer ensures that its value should always be read from the main memory and the thread should not use the cached value of that variable from their own stack. With the introduction of the Java memory model from Java 5 onwards along with the introduction of CountDownLatch, CyclicBarrier, Semaphore, and ConcurrentHashMap.
The volatile variable in Java is a special variable that is used to signal threads and compilers and runtime optimizers like JIT that the value of this particular variable is going to be updated by multiple threads inside the Java application. By making a variable volatile using the volatile keyword in Java, the application programmer ensures that its value should always be read from the main memory and the thread should not use the cached value of that variable from their own stack. With the introduction of the Java memory model from Java 5 onwards along with the introduction of CountDownLatch, CyclicBarrier, Semaphore, and ConcurrentHashMap.
Difference between synchronized block and method in Java? Thread Example
Synchronized block and synchronized methods are two ways to use synchronized keywords in Java and implement mutual exclusion on critical sections of code. Since Java is mainly used to write multi-threading programs, which present various kinds of thread-related issues like thread-safety, deadlock, and race conditions, which plagues into code mainly because of poor understanding of the synchronization mechanism provided by the Java programming language. Java provides inbuilt synchronized and volatile keywords to achieve synchronization in Java. The main difference between the synchronized method and the synchronized block is a selection of locks on which critical section is locked.
Producer Consumer Problem with Wait and Notify - Thread Example Tutorial
The Producer-Consumer Problem is a classical concurrency problem and in fact, it is one of the most powerful concurrency design patterns which is used in most multithreaded Java applications. In the last article, I have shown you how to solve the Producer-Consumer problem in Java using blocking Queue but one of my readers emailed me and requested a code example and explanation of solving the Producer-Consumer problem in Java with the wait and notify method as well Since it's often asked as one of the top coding questions in Java. In this Java tutorial, I have put the code example of the wait notify version of the earlier producer-consumer concurrency design pattern.
Java CountDownLatch Example for Beginners - [Multithreading Tutorial]
Hello Java programmers, the CountDownLatch is an important concurrency utility class that was added in JDK 1.5 to facilitate inter-thread communication without using wait and notify methods, but unfortunately, many Java developers still struggle to understand and use this powerful tool. In this article, you will learn what is CountDownLatch and how to use it to write better concurrent applications in Java. You can use the CountDownLatch if you are spawning multiple threads to do different jobs and want to know when exactly all tasks are finished so that you can move to the next stage. In other words, you can block a thread until other threads complete their task.
How to do Inter process communication in Java? MemoryMapped File Example Tutorial
Hello guys, in the past, I have shown you how to do inter-thread communication in Java using wait-notify, and today, I will teach you how to do inter-process communication in Java. There are many ways to do inter-process communication in Java, you can use Sockets, both TCP and UDP, you can use RMI (Remote Method Invocation), you can use web services, or you can use memory-mapped file. The socket is the most common way of achieving inter-process communication if two processes are in two different hosts and connected via a network. RMI and WebService can also be used for similar purposes, but the last one, inter-process communication using memory-mapped files, is particularly useful if you are communicating with other processes in the same host, sharing the same memory and file system.
Why wait() and notify() method should be called inside a loop in Java? Example
Hello Java programmers, if you have used the wait() and notify() method in Java then you know that the standard idiom of calling the wait() method uses a loop, but have you ever thought why? This is even advised by none other than Joshua Bloch, a Java guru and author of the popular Effective Java book, a must-read for any Java programmer. When I first started using this method, I was puzzled why not just use the if block because ultimately we are testing for a condition and then either waiting or going for further processing. An if block is more readable for the testing condition than a while loop like for the classic producer-consumer problem, the waiting condition for producer thread could be written as :
Java CyclicBarrier Example for Beginners [Multithreading Tutorial]
This is the second part of my concurrency tutorial, in the first part, you have learned how to use CountDownLatch and in this part, you will learn how to use CyclicBarrier class in Java. CyclicBarrier is another concurrency utility introduced in Java 5 which is used when a number of threads (also known as parties) want to wait for each other at a common point, also known as the barrier before starting processing again. It's similar to the CountDownLatch but instead of calling countDown() each thread calls await() and when the last thread calls await() which signals that it has reached the barrier, all threads started processing again, also known as a barrier is broken.
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