Java Reference
In-Depth Information
features from its superclass. Furthermore, the subclass can add new features of its own.
Therefore, rather than create completely new classes from scratch, you can take advantage of
inheritance and reduce software complexity.
Inheritance can be viewed as a treelike, or hierarchical, structure wherein a superclass is
shown with its subclasses. Consider the diagram in Figure 10-1, which shows the
relationship between various shapes.
Shape
Circle
Rectangle
Square
FIGURE 10-1 Inheritance hierarchy
In this diagram, Shape is the superclass. The class es Circle and Rectangle are
derived from Shape , and the class Square is derived from Rectangle . Every
Circle and every Rectangle is a Shape . Every Square is a Rectangle .
The general syntax to derive a class from an existing class is:
1
0
modifier(s) class ClassName extends ExistingClassName modifier(s)
{
memberList
}
In Java, extends is a reserved word.
EXAMPLE 10-1
Suppose that we have defined a class called Shape . The following statements specify
that the class Circle is derived from Shape :
public class Circle extends Shape
{
.
.
.
}
 
Search WWH ::




Custom Search