What Volatile 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. It means that multiple threads can use a method and instance of the classes at the same time without any problem.

What is volatile and non volatile in Java?

In volatile memory, the program's data are stored which are currently in process by the CPU. In non-volatile memory, any kind of data which has to be saved permanently are stored.

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.