Java Reference
In-Depth Information
delegation
—the stack method invoked delegates the call to the appropriate
List<T>
method. In particular,
StackComposition<T>
delegates calls to
List<T>
methods
insert-
AtFront
,
removeFromFront
,
isEmpty
and
print
. In this example, we do not show class
StackCompositionTest
, because the only difference is that we change the type of the stack
from
StackInheritance
to
StackComposition
(lines 3 and 10 of Fig. 21.11).
1
// Fig. 21.12: StackComposition.java
2
// StackComposition uses a composed List object.
3
package
com.deitel.datastructures;
4
5
public class
StackComposition<T>
6
{
7
private
List<T> stackList;
8
9
// constructor
10
public
StackComposition()
11
{
12
stackList =
new
List<T>(
"stack"
);
13
}
14
15
// add object to stack
16
public void
push(T object)
17
{
18
stackList.insertAtFront(object);
19
}
20
21
// remove object from stack
22
public
T pop()
throws
EmptyListException
23
{
24
return
stackList.removeFromFront();
25
}
26
27
// determine if stack is empty
28
public
boolean
isEmpty()
29
{
30
return
stackList.isEmpty();
31
}
32
33
// output stack contents
34
public void
print()
35
{
36
stackList.print();
37
}
38
}
// end class StackComposition
Fig. 21.12
|
StackComposition
uses a composed
List
object.
Another commonly used data structure is the queue
.
A queue is similar to a checkout line
in a supermarket—the cashier services the person at the
beginning
of the line
first
. Other
customers enter the line only at the end and wait for service.
Queue nodes are removed only
from the head (or front) of the queue and are inserted only at the tail (or end).
For this reason,
