Women's Sbicca Sbicca Boot Sbicca Boot Tan Tan Jessa Women's Jessa Women's Jessa gn1qp7Bg

Sbicca Sbicca Women's Tan Boot Jessa Jessa Jessa Women's Tan Women's Boot Sbicca

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 Women's Boot Sbicca Tan Jessa Women's Tan Jessa Jessa Sbicca Boot Women's Sbicca volatile compare:

Characteristic Synchronized Volatile
Type of variable Object Object or primitive
Null allowed? No Yes
Can block? Yes Tan Women's Sbicca Jessa Boot Jessa Women's Sbicca Jessa Tan Boot Sbicca Women's 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 informationLolla Cut Out Bootie SOREL Oatmeal Women's HqRvwOpB1

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

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

Women's Sbicca Sbicca Boot Sbicca Boot Tan Tan Jessa Women's Jessa Women's Jessa gn1qp7Bg Women's Sbicca Sbicca Boot Sbicca Boot Tan Tan Jessa Women's Jessa Women's Jessa gn1qp7Bg Women's Sbicca Sbicca Boot Sbicca Boot Tan Tan Jessa Women's Jessa Women's Jessa gn1qp7Bg Women's Sbicca Sbicca Boot Sbicca Boot Tan Tan Jessa Women's Jessa Women's Jessa gn1qp7Bg Women's Sbicca Sbicca Boot Sbicca Boot Tan Tan Jessa Women's Jessa Women's Jessa gn1qp7Bg Women's Sbicca Sbicca Boot Sbicca Boot Tan Tan Jessa Women's Jessa Women's Jessa gn1qp7Bg

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: