In the Java example below, the method getArea is defined within the class rectangle. In order for the getArea method to be used by a program, an object must first be created from the rectangle class.
int getArea(int width, int height)
int area = width * height;
Methods are an important part of object-oriented programming since they isolate functions to individual objects. The methods within a class can only be called by objects created from the class. Additionally, methods can only reference data known to the corresponding object. This helps isolate objects from each other and prevents methods within one object from affecting other objects.
While methods are designed to isolate data, they can still be used to return values to other classes if necessary. If a value needs to be shared with another class, the return statement (as seen in the example above) can be used.