What is AtomicInteger and when to use?

Asked By: Valdete Aichmeier | Last Updated: 29th February, 2020
Category: technology and computing databases
4.2/5 (327 Views . 9 Votes)
The primary use of AtomicInteger is when you are in a multithreaded context and you need to perform thread safe operations on an integer without using synchronized . The assignation and retrieval on the primitive type int are already atomic but AtomicInteger comes with many operations which are not atomic on int .

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Besides, what is the use of AtomicInteger?

Among them, the AtomicInteger class is a wrapper class for an int value that allows it to be updated atomically. The class provides useful methods, some of which will be shown in the code snippet below. The most common use of the AtomicInteger is to handle a counter that is accessed by different threads simultaneously.

Also, what is an atomic integer? The AtomicInteger class provides you with a int variable which can be read and written atomically, and which also contains advanced atomic operations like compareAndSet() . The AtomicInteger class is located in the java. util. concurrent. atomic package, so the full class name is java.

Similarly, it is asked, is AtomicInteger thread safe?

AtomicInteger uses sun. misc. Unsafe underneath to perform the atomic updates. So, in answer to your question, yes, AtomicInteger is thread-safe.

What are atomic classes in Java?

Atomic Variables in Java. The most commonly used atomic variable classes in Java are AtomicInteger, AtomicLong, AtomicBoolean, and AtomicReference. These classes represent an int, long, boolean and object reference respectively which can be atomically updated.

34 Related Question Answers Found

Why volatile is used in Java?

Volatile Keyword in Java. Volatile keyword is used to modify the value of a variable by different threads. It is also used to make classes thread safe. The volatile keyword does not cache the value of the variable and always read the variable from the main memory.

What is atomic variable?

You can think of these are wrapper of primitive types boolean, integer and long, with the difference: they are designed to be safely used in multi-threaded context. They are called atomic variables because they provide some operations that cannot be interfered by multiple threads.

What is atomic Boolean?

atomic. AtomicBoolean. compareAndSet() is an inbuilt method in java that sets the value to the passed value in the parameter if the current value is equal to the expected value which is also passed in the parameter. The function returns a boolean value which gives us an idea if the update was done or not.

Is AtomicInteger volatile?

volatile AtomicInteger count; the volatile part means that each thread will use the latest AtomicInteger reference, and the fact that it's an AtomicInteger means that you'll also see the latest value for that object.

What is a CountDownLatch?

As per java docs, CountDownLatch is a synchronization aid that allows one or more threads to wait until a set of operations being performed in other threads completes. CountDownLatch concept is very common interview question in java concurrency, so make sure you understand it well.

How does AtomicInteger work in Java?

The AtomicInteger class protects an underlying int value by providing methods that perform atomic operations on the value. It shall not be used as a replacement for an Integer class. The AtomicInteger class is part of the java. atomic package since Java 1.5.

What is Java volatile?

Essentially, volatile is used to indicate that a variable's value will be modified by different threads. Declaring a volatile Java variable means: Access to the variable acts as though it is enclosed in a synchronized block, synchronized on itself.

What is atomic operation?

Definition - What does Atomic Operation mean? Atomic operations in concurrent programming are program operations that run completely independently of any other processes. Atomic operations are used in many modern operating systems and parallel processing systems.

Is increment Atomic?

4 Answers. The increment-memory machine instruction on an X86 is atomic only if you use it with a LOCK prefix. x++ in C and C++ doesn't have atomic behavior. If you want to increment a "large value" (say, a multiprecision integer), you need to do so with using some standard locking mechanism such as a semaphore.

How is thread safe counter implemented?

What is the best way to implement a thread-safe Integer Counter ?
  • You may take into account the following JAVA features. Using a static volatile int like : volatile int num = 0; –> NOT WORKING. Use a synchronized method.
  • The Java volatile keyword guarantees visibility of changes to variables across threads.
  • Using volatile is not enough to create thread safe code.

Are atomic variables thread safe?

atomic which offers lock-free and thread-safe classes. Variables of these class types are called as atomic variables. The operations provided by these classes are not only atomic but also volatile. The modifications done to atomic variables by a thread are immediately visible to other threads.

Is int atomic in Java?

For the purposes of the Java programming language memory model, a single write to a non-volatile long or double value is treated as two separate writes: one to each 32-bit half. This seems to imply that writes to ints are atomic.

What is an atomic variable in C?

atomic variable in C. In order for a variable to be "atomic", the compiler will ensure that some set of operations on that variable will be atomic, but generally those operations are limited to a single operator or function call.

What is thread safe in Java?

thread-safety or thread-safe code in Java refers to code which can safely be used or shared in concurrent or multi-threading environment and they will behave as expected. any code, class or object which can behave differently from its contract on concurrent environment is not thread-safe.

What is atomic in Java thread?

An operation is atomic when you can safely perform the operation in parallel on multiple threads without using the synchronized keyword or locks as shown in my previous tutorial. Internally, the atomic classes make heavy use of compare-and-swap (CAS), an atomic instruction directly supported by most modern CPUs.

Can volatile make a non atomic operation to Atomic?

So even though you declare variable to volatile it will not make this operation atomic, which means another thread can see a intermediate result which is a stale or unwanted value for the other thread. But AtomicInteger , AtomicReference are based on the Compare and swap instruction.

Do you need to synchronize an atomic operation?

Atomic actions cannot be interleaved, so they can be used without fear of thread interference. However, this does not eliminate all need to synchronize atomic actions, because memory consistency errors are still possible. This means that changes to a volatile variable are always visible to other threads.