Can I update other object's volatile variable directly?

Question

Say I have an object looks like this.

class Some {

    synchronized void some() {
        // do some with canceled
    }

    synchronized void setAsCanceled() {
        canceled = true;
    }

    volatile boolean canceled = false; // package-private
}

Now another object may update the canceled .

class Other {

    void setSomeAsCanceled() {
        some.canceled = true; // Not calling the setAsCanceled()
    }

    private Some some = new Some();
}

Is it safe to update the canceled volatile variable directly? Or should I call the setAsCanceled() method?

Answer 1

When a variable is created and used, it also exists in a cache. This cache isn't always in sync especially when you are using multiple threads. When you mark a variable as volatile, you are telling the system that the cache has to be updated immediately so that anyone else using it will have the updated value.