Java Reference
In-Depth Information
20
21
// remove object from queue
22
public
T dequeue()
throws
EmptyListException
23
{
24
return
queueList.removeFromFront();
25
}
26
27
// determine if queue is empty
28
public boolean
isEmpty()
29
{
30
return
queueList.isEmpty();
31
}
32
33
// output queue contents
34
public void
print()
35
{
36
queueList.print();
37
}
38
}
// end class Queue
Fig. 21.13
|
Queue
uses class
List
. (Part 2 of 2.)
Class
QueueTest
's (Fig. 21.14)
main
method creates and initializes
Queue<T>
variable
queue
(line 10). Lines 13, 15, 17 and 19 enqueue four integers, taking advantage of
auto-
boxing
to insert
Integer
objects into the queue. Lines 27-32 use an infinite loop to
dequeue the objects in first-in, first-out order. When the queue is empty, method
dequeue
throws an
EmptyListException
, and the program displays the exception's stack trace.
1
// Fig. 21.14: QueueTest.java
2
// Class QueueTest.
3
import
com.deitel.datastructures.Queue;
4
import
com.deitel.datastructures.EmptyListException;
5
6
public class
QueueTest
7
{
8
public static void
main(String[] args)
9
{
10
Queue<Integer> queue =
new
Queue<>();
11
12
// use enqueue method
queue.enqueue(
-1
);
queue.print();
queue.enqueue(
0
);
queue.print();
queue.enqueue(
1
);
queue.print();
queue.enqueue(
5
);
queue.print();
13
14
15
16
17
18
19
20
21
Fig. 21.14
|
Queue processing program. (Part 1 of 2.)
