Java Reference
In-Depth Information
/** Gets the size of this priority queue.
@return the number of entries currently in the priority queue */
public
int
getSize();
/** Removes all entries from this priority queue */
public
void
clear();
}
// end PriorityQueueInterface
Question 4
After the following statements execute, what string is at the front of the prior-
ity queue and what string is at the back?
PriorityQueueInterface<String> myPriorityQueue =
new
LinkedPriorityQueue<String>();
myPriorityQueue.add("Jane");
myPriorityQueue.add("Jim");
myPriorityQueue.add("Jill");
String name = myPriorityQueue.remove();
myPriorityQueue.add(name);
myPriorityQueue.add("Jess");
Professors and bosses like to assign tasks for us to do by certain dates. Using a priority queue,
organize these assignments in the order in which we should complete them.
10.20
To keep our example simple, we will order the assignments by their due dates. A task with the earliest
due date will have the highest priority.
We can define a class
Assignment
of tasks that includes a data field
date
representing a task's due
date. Figure 10-12 shows a diagram of such a class. We assume that
date
is an instance of a
Comparable
class such as
java.sql.Date
in the Java Class Library. Thus,
date.compareTo(otherDate)
is negative,
for example, if
date
occurs before
otherDate
. The
compareTo
method for
Assignment
is then
public int
compareTo(Assignment other)
{
return
-date.compareTo(other.date);
}
// end compareTo
A more sophisticated version of
Assignment
could include other criteria in
compareTo
to assess priority.
FIGURE 10-12
A diagram of the class
Assignment
Assignment
course
—the course code
task
—a description of the assignment
date
—the due date
getCourseCode()
getTask()
getDueDate()
compareTo()
