What are the characteristics of CAS in Java?

The characteristics of CAS (Compare and Swap) in Java are:

1. Atomicity: CAS operation is atomic, meaning that during the execution of the CAS operation, it will not be interrupted by other threads, ensuring the integrity of the operation.
2. Lock-Free: CAS operation does not require the use of locks, but instead utilizes underlying hardware support to achieve atomic operations, thus avoiding the overhead of locks and thread blocking.
3. Optimistic concurrency control: CAS operation is an optimistic way of concurrency control, assuming that conflicts are rare when modifying shared variables. As a result, it does not block other threads’ operations but instead checks whether the value of the shared variable is the same as the expected value during the update. If they are the same, it updates, otherwise it retries.
4. Reduce the number of thread switches: CAS operations do not require switching threads to kernel mode during execution, reducing the number of thread switches and improving performance.
5. Solving the ABA problem: CAS operations can resolve the ABA problem by checking the value of the shared variable before performing the operation, thus avoiding misjudgment.

Although CAS operations have the advantages mentioned above, there are also some drawbacks such as it not being able to resolve issues like long cycle times and high CPU consumption. Therefore, in practical applications, it is necessary to choose the appropriate concurrency control method based on specific circumstances.