Interfaces and Inner Classes - Java - page 690

Display 13.11 Anonymous Classes (part 2 of 2)

26 public int getNumber()

27 {

28 return number;

29 }

30 };

31 anObject.setNumber(42);

32 anotherObject.setNumber(42);

33 showNumber(anObject);

34 showNumber(anotherObject);

35 System.out.println("End of program.");

36 }

public static void showNumber(NumberCarrier o) 37

38 {

39 System.out.println(o.getNumber());

40 }

This is the file AnonymousClassDemo.java .

41 }

Sample Dialogue
42
84
End of program.

This is the file NumberCarrier.java . 1 public interface NumberCarrier

2{
3 public void setNumber( int value);
4 public int getNumber();
5}

TIP: Why Use Inner Classes?

Most simple situations do not need inner classes. However, there are situations for
which inner classes are a good solution. For example, suppose you want to have a class
with two base classes. That is not allowed in Java. However, you can have an outer
class derived from one base class with an inner class derived from the other base class.
Since the inner and outer classes have access to each other's instance variables and
methods, this can often serve as if it were a class with two base classes.