Why is volatile used in Java?

Why is volatile used 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 volatile in Java?

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.

Is volatile necessary Java?

Yes, volatile must be used whenever you want a mutable variable to be accessed by multiple threads. It is not very common usecase because typically you need to perform more than a single atomic operation (e.g. check the variable state before modifying it), in which case you would use a synchronized block instead.

What is Singleton and double locking?

In double-checked locking, code checks for an existing instance of Singleton class twice with and without locking to make sure that only one instance of singleton gets created.

How can Singleton be broken?

Serialization is used to convert an object of byte stream and save in a file or send over a network. Suppose you serialize an object of a singleton class. Then if you de-serialize that object it will create a new instance and hence break the singleton pattern.

What does the ‘volatile’ keyword mean in Java?

The Java volatile keyword is used to mark a Java variable as “being stored in main memory”. More precisely that means, that every read of a volatile variable will be read from the computer’s main memory, and not from the CPU cache , and that every write to a volatile variable will be written to main memory, and not just to the CPU cache.

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.

    What do volatile keywords do in Java?

    Changes to volatile variables are not cached in registers or other cache where they are hidden from other threads.

  • Compiler and runtime do not reorder the operations with other memory operations for volatile variables (aka no optimzation will be done).
  • Reads and writes are atomic for all variables that are declared volatile.