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javamultithreading
John
John

Reputation: 4028

Multiple threads get value of x variable but only one thread can change the value of x variable at a time

In Java, I have a global variable x, what should I use to allows many threads get the value of x at a time but only one thread can change the value of x variable at a time?

Any example? Thanks.

Upvotes: 0

Views: 857

Answers (3)

Anoop
Anoop

Reputation: 1845

You can use a ReadWriteLock to acheive this. Java java.util.concurrent.locks package provides different types of locks. You can use ReentrantReadWriteLock from this package. Code samples can be found in javadoc.

If the global variable is a basic data type, AtomicLong, AtomicInt etc in java.util.concurrent.atomic package should also be able to solve the usecase.

Upvotes: 1

Geoff Reedy
Geoff Reedy

Reputation: 36011

In this case you should be able to use the classes in java.util.concurrent.atomic. These classes are containers for a single value that allow lock-free access. If you don't need a compare-and-swap operation you can use a volatile field as long as you're using at least java 1.5.

Upvotes: 1

Michael Aaron Safyan
Michael Aaron Safyan

Reputation: 95489

If you want to allow multiple concurrent reads, then you will want to use a ReadWriteLock (the ReentrantReadWriteLock class implements that particular interface) to protect access.

Upvotes: 1

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