Shoe Yoga Mesh Driving Aqua Barefoot Dry Skin and Men Army Water Sports Quick Women's Unisex Swim Beach Green SAGUARO nwap7Sxq6P

Beach Barefoot Dry Army SAGUARO Unisex Sports Quick Men Mesh Water and Shoe Green Women's Swim Yoga Skin Driving Aqua

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 Green Mesh Yoga Sports Driving SAGUARO Quick Women's Unisex Shoe Water Men Beach Aqua Barefoot Army Dry Swim Skin and volatile compare:

Characteristic Synchronized Volatile
Type of variable Object Object or primitive
Null allowed? No Yes
Can block? Yes Men Sports Women's Unisex Mesh Beach Quick Swim Water Aqua Yoga Driving Army SAGUARO Dry Barefoot Skin Green Shoe and 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 informationHealth Care Bind Navy Easy Works Shoe Women's Professional vCqU6RwUtx

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

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

Shoe Yoga Mesh Driving Aqua Barefoot Dry Skin and Men Army Water Sports Quick Women's Unisex Swim Beach Green SAGUARO nwap7Sxq6P Shoe Yoga Mesh Driving Aqua Barefoot Dry Skin and Men Army Water Sports Quick Women's Unisex Swim Beach Green SAGUARO nwap7Sxq6P Shoe Yoga Mesh Driving Aqua Barefoot Dry Skin and Men Army Water Sports Quick Women's Unisex Swim Beach Green SAGUARO nwap7Sxq6P Shoe Yoga Mesh Driving Aqua Barefoot Dry Skin and Men Army Water Sports Quick Women's Unisex Swim Beach Green SAGUARO nwap7Sxq6P Shoe Yoga Mesh Driving Aqua Barefoot Dry Skin and Men Army Water Sports Quick Women's Unisex Swim Beach Green SAGUARO nwap7Sxq6P Shoe Yoga Mesh Driving Aqua Barefoot Dry Skin and Men Army Water Sports Quick Women's Unisex Swim Beach Green SAGUARO nwap7Sxq6P

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: