Prentice.Hall.Introduction.to.Java.Programming,.Brief.Version.9th.(2014).[sharethefiles.com]

584 Chapter 15 Abstract Classes and Interfaces
public static void eat(Edible stuff) {
stuff.howToEat();
}
Edible interface
Chicken class
Duck class
Broccoli class
interface Edible {
public String howToEat() ;
}
class Chicken implements Edible {
@Override
public String howToEat() {
return "Fry it";
}
}
class Duck implements Edible {
@Override
public String howToEat() {
return "Roast it";
}
}
class Broccoli implements Edible {
@Override
public String howToEat() {
return "Stir-fry it";
}
}
To define a class that represents edible objects, simply let the class implement the Edible
interface. The class is now a subtype of the Edible type, and any Edible object can be
passed to invoke the eat method.
✓Point✓ Check
15.27 Give an example to show why interfaces are preferred over abstract classes.
15.28 Define the terms abstract classes and interfaces. What are the similarities and differences
between abstract classes and interfaces?
15.28 True or false?
a. An interface is compiled into a separate bytecode file.
b. An interface can have static methods.
c. An interface can extend one or more interfaces.
d. An interface can extend an abstract class.
e. An abstract class can extend an interface.
Key
Point
15.9 Case Study: The Rational Class
This section shows how to design the Rational class for representing and processing
rational numbers.
A rational number has a numerator and a denominator in the form a/b, where a is the numerator
and b the denominator. For example, 1/3, 3/4, and 10/4 are rational numbers.
A rational number cannot have a denominator of 0, but a numerator of 0 is fine. Every integer
i is equivalent to a rational number i/1. Rational numbers are used in exact computations
involving fractions—for example, 1/3 = 0.33333. . . . This number cannot be precisely
represented in floating-point format using either the data type double or float. To obtain
the exact result, we must use rational numbers.