Inheritance - Java Software Solutions: Foundations of Program Design - page 446

LISTING 9.1
//********************************************************************
// Words.java Author: Lewis/Loftus
//
// Demonstrates the use of an inherited method.
//********************************************************************
public class Words
{
//-----------------------------------------------------------------
// Instantiates a derived class and invokes its inherited and
// local methods.
//-----------------------------------------------------------------
public static void main (String[] args)
{
Dictionary webster = new Dictionary();
System.out.println ("Number of pages: " + webster.getPages());
System.out.println ("Number of definitions: " +
webster.getDefinitions());
System.out.println ("Definitions per page: " +
webster.computeRatio());
}
}
OUTPUT
Number of pages: 1500
Number of definitions: 52500
Definitions per page: 35.0
version of the parent class. A dictionary has pages, because all books have pages;
but although a dictionary has definitions, not all books do.
Inheritance relationships are often represented in UML class diagrams. Figure 9.1
shows the inheritance relationship between the Book and Dictionary classes. An
arrow with an open arrowhead is used to show inheritance in a UML diagram,
with the arrow pointing from the child class to the parent class.