When you develop an application in Java using object-oriented programming, you create some classes formed by attributes and methods. The methods of a class determine the operations that you can do with the class. Attributes store the data that defines the object. Normally, in each class, you implement some methods to establish the value of the attributes. Also, objects change as the application runs, and you use those methods to change the value of their attributes.
When you develop a concurrent application, you have to pay special attention to the objects shared by more than one thread. You must use a synchronization mechanism to protect access to such objects. If you don't use it, you may have data inconsistency problems in your application.
There are special kinds of objects that you can implement when you work with concurrent applications. They are called immutable...
