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Is volatile variable in Java thread safe?

Is volatile variable in Java thread safe?

Access to volatile int in Java will be thread-safe.

Where are volatile variables stored in Java?

Volatile fields are instance or class (static) variables and are stored in the heap.

What is volatile in Java with example?

Using volatile is yet another way (like synchronized, atomic wrapper) of making class thread safe. Thread safe means that a method or class instance can be used by multiple threads at the same time without any problem. Consider below simple example.

What does Java volatile mean?

volatile means that the variable changes at runtime and that the compiler should not cache its value for any reason. This is only really a problem when sharing the variable amongst threads, you don’t want a thread working with stale data, so the compiler should never cache the value of a volatile variable reference.

What is the difference between static and volatile variable?

volatile variable value access will be direct from main memory. It should be used only in multi-threading environment. static variable will be loaded one time. If its used in single thread environment, even if the copy of the variable will be updated and there will be no harm accessing it as there is only one thread.

What is the purpose of a volatile variable?

Volatile keyword is used to modify the value of a variable by different threads. It is also used to make classes thread safe. It means that multiple threads can use a method and instance of the classes at the same time without any problem. The volatile keyword can be used either with primitive type or objects.

Why volatile is used in Singleton?

The volatile prevents memory writes from being re-ordered, making it impossible for other threads to read uninitialized fields of your singleton through the singleton’s pointer.

Can we use static volatile?

Even if the static variables are shared variables, but in different thread there can be different values for a static variable in the local cache of a thread. To make it consistent for all threads, just declare it as static volatile . So each time it will fetch from main memory.

Can we use volatile without static?

Yes, you can. A static variable in Java is stored once per class (not once per object, such as non-static variables are). Declaring a variable as volatile (be it static or not) states that the variable will be accessed frequently by multiple threads.

Why is volatile needed?

The volatile field is needed to make sure that multiple threads always see the newest value, even when the cache system or compiler optimizations are at work. Reading from a volatile variable always returns the latest written value from this variable.

Is enum singleton thread safe?

Creation of Enum instance is thread-safe By default, the Enum instance is thread-safe, and you don’t need to worry about double-checked locking. In summary, the Singleton pattern is the best way to create Singleton in Java 5 world, given the Serialization and thread-safety guaranteed and with some line of code enum.

What is static and volatile variables?

A static variable refers to a class variable that’s shared among all instances. volatile: Volatile variables are those which are read and written to main memory. They aren’t stored in local cache and are always fetched from main memory.

When to use volatile Java?

The most common use for volatile variables in Java is to use it as a completion, interruption, or status flag. So let’s see an example where we have a status flag.

What is volatile and transient variable in Java?

transient variables are used to prevent serialization or a field while volatile variables are used to prevent reordering and avoid reading cached value of field in multithreaded Java program. Only similarity between transient and volatile keyword is that they are only applicable to field or properties of class.

When to use volatile?

we have two application threads: the main thread and the reader thread.

  • the reader thread may see those writes in any order other than the actual program order.
  • 3.3. volatile Memory Order.
  • What does the modifier volatile in Java do?

    What does the modifier volatile in Java do? The volatile modifier is used to let the JVM know that a thread accessing the variable must always merge its own private copy of the variable with the master copy in the memory. Accessing a volatile variable synchronizes all the cached copied of the variables in the main memory.