Java Reference
In-Depth Information
EXAMPLE:
(continued)
The class
Money
is a private inner class of the class
BankAccount
. So, the class
Money
cannot be used outside of the class
BankAccount
. (Public inner classes are discussed in
Section 13.3 and have some subtleties involved in their use.) Since the class
Money
is
local to the class
BankAccount
, the name
Money
can be used for the name of another
class outside of the class
BankAccount
. (This would be true even if
Money
were a public
inner class.)
We have made the instance variables in the class
Money
private
following our usual
conventions for class members. When we discuss public inner classes, this will be
important. However, for use within the outer class (and a private inner class cannot be
used anyplace else), there is no difference between
public
and
private
or other mem-
ber modifiers. All instance variables and all methods of the inner class are public to the
outer class no matter whether they are marked
public
or
private
or anything else.
Notice the method
closeAccount
of the outer class. It uses the private instance vari-
ables
dollars
and
cents
of the inner class.
This is still very much a toy example, but we will have occasion to make serious use
of private inner classes when we discuss linked lists in Chapter 15 and when we study
Swing GUIs starting in Chapter 17.
Display 13.9
Class with an Inner Class
(part 1 of 2)
1
public class BankAccount
2{
3
private class
Money
The modifier
private
in this line
should not be changed to
public
.
However, the modifiers
public
and
private
inside the inner class
Money
can be changed to anything else and
it would have no effect on the class
BankAccount
.
4
{
5
private long
dollars;
6
private int
cents;
7
public
Money(String stringAmount)
8
{
9
abortOnNull(stringAmount);
10
int
length = stringAmount.length();
11
dollars = Long.parseLong(
−
3));
12
stringAmount.substring(0, length
13
cents = Integer.parseInt(
−
2, length));
14
stringAmount.substring(length
15
}
16
public
String getAmount()
17
{
18
if
(cents > 9)
