Classes are the core of object-oriented programming languages, such as Java. Applets or applications developed in Java are built around objects, which are reusable components of code that include methods and properties. Methods are tasks that can be performed on objects. Properties are characteristics of an object that you can access directly.
Each object is an instance of a class of objects. GUI objects in Java, for example, may belong to such classes as Menu, Dialog, and Checkbox. Each class defines the methods and properties for objects that are part of that class. For example, the JavaAwtCheckBox class defines the methods and properties for all Java Abstract Windowing Toolkit check boxes. The methods and properties defined for JavaAwtCheckboxes work only on these check boxes, not on other Java objects.