The role of volatile in java

volatile keyword ensures the visibility and ordering of multi-thread shared variables: Visibility: Modifications to volatile variables are immediately reflected in other threads. Orderliness: The order of volatile variable operations is consistent with the program order.

The role of volatile in Java

The volatile keyword is used to ensure that shared variables are maintained across multiple threads Visibility and order. It is implemented in the following ways:

1. Visibility

• When one thread modifies a volatile variable, it is immediately reflected in all other threads.
• This is because volatile variables are forced to be read and written from main memory instead of being stored in each thread's own CPU cache.

2. Orderliness

• #The read and write operations of volatile variables are ordered, which means that every time a read or write operation is performed It will all be done in the order in the program.
• This makes multiple-write-single-read operations consistent, and writes that occur on volatile variables are not visible until subsequent read operations.

Usage

To declare a variable as volatile in Java, add the volatile keyword before the variable type:

volatile int count;

When to use

volatile variables are usually used in the following situations:

• Multiple threads access shared variables simultaneously.
• The value of the variable needs to be consistent across all threads.
• A variable contains a reference to another resource that is shared among multiple threads.

Notes

• volatile does not prevent thread conflicts or data races.
• The reading and writing of volatile variables are still subject to the Java memory model.
• The performance overhead of volatile variables is usually small, but in some cases it may affect performance.

The above is the detailed content of The role of volatile in java. For more information, please follow other related articles on the PHP Chinese website!