Explain the use of volatile variable. ?

Hi Abhishek,
Java Memory model defines the possible rules for threads and the expected behavior of multi-threaded programs so that programmers can design their programs accordingly. JSR-133 describes the semantics of threads, locks, volatile variables and data races.

Volatile variables are treated different from other variables. When you mark a variable as volatile, this warns the compiler to get fresh copies of the variable rather than caching the variable in the registers.

Volatile variables can be used to store shared variables at a lower cost than that of synchronization, but they have limitations. While writes to volatile variables are guaranteed to be immediately visible to other threads (because JVM does not allow threads to cache volatile variables), there is no way to render a read-modify-write sequence of operations atomic, meaning, for example, that a volatile variable cannot be used to reliably implement a mutex (mutual exclusion lock) or a counter.


Please refer the below links

http://ilkinbalkanay.blogspot.in/2007/10/volatile-variables-in-java.html

http://www.javamex.com/tutorials/synchronization_volatile.shtml

http://en.wikipedia.org/wiki/Volatile_variable

http://www.cs.princeton.edu/courses/archive/spr96/cs333/java/tutorial/java/javaOO/volatile.html

Thanks

Hi Abhishek,

Volatile keyword

        The volatile is a keyword defined in the java programming language. Keywords are basically reserved words which have specific meaning relevant to a compiler in java programming language likewise the volatile keyword indicates the following :

-- The volatile keyword is mostly used to indicate that a member variable of a class may get modified asynchronously by more than one thread.
-- This thing is noticeable that the volatile keyword is not implemented in many Java Virtual Machines.
-- The volatile keyword from the side of compiler tries to guarantee that all the threads should see the same value of a specified variable.

        Generally speaking, the volatile keyword is intended to prevent the compiler from applying any optimizations on the code that assume values of variables cannot change "on their own."

Example,

public class Test
{
        volatile int sharableValue;
}

Thanks & Regards
----------------
Chintan Rathod