Atomic classes

Atomic classes enclose primitive values into objects and provide atomic operations on them. We discussed race conditions and volatile variables. For example, if we have an int variable to be used as a counter and we want to assign a unique value to objects that we work with, we can increment the value and use the result as a unique ID. However, when multiple threads use the same code, we cannot be sure about the value we read after the increment. It may happen that another thread also incremented the value in the meantime. To avoid that, we will have to enclose the increment and the assignment of the incremented value to an object into a synchronized block. This can also be done using AtomicInteger.

If we have a variable of AtomicInteger, then calling incrementAndGet increments the value of int enclosed in the class and returns the incremented value. Why do it instead of using synchronized block? The first answer is that if the functionality is there in the JDK, then using...