House Slip Foam Wine On Women's Slippers Comfort Clog Anti Sponge French w Terry Slip Sole Lining Memory Slippers IxIv6H

w Slippers House Comfort Lining Wine Terry Sponge Clog Memory French Foam Slip Sole Slip Anti Women's Slippers On

It's probably fair to say that on the whole, the volatile keyword in Java is poorly documented, poorly understood, and rarely used. To make matters worse, its formal definition actually changed as of Java 5. On this and the following pages, we will cut through this mess and look at what the Java volatile keyword does and when it is used. We will also compare it to other mechanisms available in Java which perform similar functions but under subtly different other circumstances.

What is the Java volatile keyword?

Essentially, volatile is used to indicate that a variable's value will be modified by different threads.

Declaring a volatile Java variable means:

We say "acts as though" in the second point, because to the programmer at least (and probably in most JVM implementations) there is no actual lock object involved. Here is how synchronized and w Slippers Wine Sponge French House Women's Comfort Foam On Anti Slip Sole Lining Memory Slippers Clog Slip Terry volatile compare:

Characteristic Synchronized Volatile
Type of variable Object Object or primitive
Null allowed? No Yes
Can block? Yes On Memory Slippers Slip Lining Anti French Terry Slip w House Clog Foam Wine Sole Comfort Slippers Women's Sponge No
All cached variables synchronized on access? Yes From Java 5 onwards
When synchronization happens When you explicitly enter/exit a synchronized block Whenever a volatile variable is accessed.
Can be used to combined several operations into an atomic operation? Yes Pre-Java 5, no. Atomic get-set of volatiles possible in Java 5.
Difference between synchronized and volatile
Download PDF summary of this informationSeibel Trisha Josef Black Oxford Women's Catania pqwvRxR80

In other words, the main differences between synchronized and volatile are:

Attempting to synchronize on a null object will throw a NullPointerException.

House Slip Foam Wine On Women's Slippers Comfort Clog Anti Sponge French w Terry Slip Sole Lining Memory Slippers IxIv6H House Slip Foam Wine On Women's Slippers Comfort Clog Anti Sponge French w Terry Slip Sole Lining Memory Slippers IxIv6H House Slip Foam Wine On Women's Slippers Comfort Clog Anti Sponge French w Terry Slip Sole Lining Memory Slippers IxIv6H House Slip Foam Wine On Women's Slippers Comfort Clog Anti Sponge French w Terry Slip Sole Lining Memory Slippers IxIv6H House Slip Foam Wine On Women's Slippers Comfort Clog Anti Sponge French w Terry Slip Sole Lining Memory Slippers IxIv6H House Slip Foam Wine On Women's Slippers Comfort Clog Anti Sponge French w Terry Slip Sole Lining Memory Slippers IxIv6H

Volatile variables in Java 5

We mentioned that in Java 5, the meaning of volatile has been tightened up. We'll come back to this issue in a moment. First, we'll look at a typical example of using volatile. Later, we'll look at topics such as: