What is considered thread-safe?

“A class is thread-safe if it behaves correctly when accessed from multiple threads, regardless of the scheduling or interleaving of the execution of those threads by the runtime environment, and with no additional synchronization or other coordination on the part of the calling code.”

What is C++ thread-safe?

An object is thread-safe for reading from multiple threads. For example, given an object A, it is safe to read A from thread 1 and from thread 2 simultaneously. It’s safe to read and write to one instance of a type even if another thread is reading or writing to a different instance of the same type.

When should I worry about thread safety?

If you pass in an object to the method and the method mutates the object and before the method completes you call the same method again on a different thread but with the same object, then you have a problem.

Is instant now thread-safe?

According to the docs for Instant under the implementation notes: This class is immutable and thread-safe.

Is ArrayList thread-safe?

ArrayList , on the other hand, is unsynchronized, making them, therefore, not thread safe. With that difference in mind, using synchronization will incur a performance hit. So if you don’t need a thread-safe collection, use the ArrayList .

Is open thread safe?

If you’re running on a Unix-like OS, when open() is a direct system call, the answer is absolutely yes. Different threads can open files (or even the same file) at the same time just as different processes can.

Is ArrayList thread safe?

Is HashMap thread safe?

HashMap is non-synchronized. It is not thread-safe and can’t be shared between many threads without proper synchronization code whereas Hashtable is synchronized.

Is mutex thread-safe?

It is totally safe for multiple threads to read the same variable, but std::mutex can not be locked by multiple threads simultaneously, even if those threads only want to read a value. Shared mutexes and locks allow this.