How To Implement Volatile Keyword in Java?

Java is one programming that is blessed with plenty of features. In this article we will be exploring one such feature that is volatile keyword in Java. Following pointers will be covered in this article,

• Volatile Keyword
• Difference between Synchronization and Volatile Keyword
• Example

Moving on with this article on Volatile Keyword in Java.

A 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.

Example

class Test
{
static int var=5;
}

In the above example, assume that two threads are working on the same class. Both threads run on different processors where each thread has its local copy of var. If any thread modifies its value, the change will not reflect in the original one in the main memory. It leads to data inconsistency because the other thread is not aware of the modified value.

class Test
{
static volatile int var =5;
}

In the above example, static variables are class members that are shared among all objects. There is only one copy in the main memory. The value of a volatile variable will never be stored in the cache. All read and write will be done from and to the main memory.

Moving on with this article on Volatile Keyword in Java.

Difference between synchronization and volatile keyword

Volatile keyword is not a substitute of synchronized keyword, but it can be used as an alternative in certain cases. There are the following differences are as follows:

Moving on with this article on Volatile Keyword in Java.

Example:

public class VolatileTest {
private static final Logger LOGGER = MyLoggerFactory.getSimplestLogger();
private static volatile int MY_INT = 0;
public static void main(String[] args) {
new ChangeListener().start();
new ChangeMaker().start();
}
static class ChangeListener extends Thread {
@Override
public void run() {
int local_value = MY_INT;
while ( local_value < 5){
if( local_value!= MY_INT){
LOGGER.log(Level.INFO,"Got Change for MY_INT : {0}", MY_INT);
local_value= MY_INT;
}
}
}
}
static class ChangeMaker extends Thread{
@Override
public void run() {
int local_value = MY_INT;
while (MY_INT <5){
LOGGER.log(Level.INFO, "Incrementing MY_INT to {0}", local_value+1);
MY_INT = ++local_value;
try {
Thread.sleep(500);
} catch (InterruptedException e) { e.printStackTrace(); }
}
}
}
}

Thus we have come to an end of this article on ‘Volatile Keyword in Java’. If you wish to learn more, check out the Java Training by Edureka, a trusted online learning company. Edureka’s Java J2EE and SOA training and certification course is designed to train you for both core and advanced Java concepts along with various Java frameworks like Hibernate & Spring.

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