Java Reference
In-Depth Information
Display 6.5
Partially Filled Array Class
(part 4 of 4)
117
public boolean
empty()
118 {
119
return
(numberUsed == 0);
120 }
121
public boolean
full()
122 {
123
return
(numberUsed == maxNumberElements);
124 }
125
public int
getMaxCapacity()
126 {
127
return
maxNumberElements;
128 }
129
130
public int
getNumberOfElements()
131 {
132
return
numberUsed;
133 }
134 }
TIP: Accessor Methods Need Not Simply Return Instance Variables
Note that in the class
PartiallyFilledArray
in Display 6.5 , there is no
accessor method that returns a copy of the entire instance variable
a
. The reason
this was not done is that, when the class is used as intended, a user of the class
PartiallyFilledArray
would have no need for the entire array
a
. That is an
implementation detail. The other methods that start with
get
allow a programmer
using the class to obtain all the data that he or she needs.
■
The “for-each” Loop
★
As you have already seen, you can use a
for
loop to cycle through all the elements in
an array. For example,
double
[] a =
new double
[10];
<Some code to fill the array
a
>
for
(
int
i = 0; i < a.length; i++)
System.out.println(a[i]);
The standard Java libraries contain definitions of a number of so-called
collection classes
.
A collection class is a class whose objects store a collection of values. You cannot cycle
