Queues, Deques, and Priority Queues - Data Structures and Abstractions with Java - page 264

public void addProject(String courseCode, String task, Date dueDate)
{

Assignment newAssignment = new Assignment(courseCode, task,
dueDate);

addProject(newAssignment);
} // end addProject

public Assignment getNextProject()
{

return log.peek();
} // end getNextProject

public Assignment removeNextProject()
{

return log.remove();
} // end removeNextProject
} // end AssignmentLog

10.22

The following statements could appear in a client of AssignmentLog :
AssignmentLog myHomework = new AssignmentLog();
myHomework.addProject("CSC211", "Pg 50, Ex 2",
Date.valueOf("2012-10-21"));
Assignment pg75Ex8 = new Assignment("CSC215", "Pg 75, Ex 8",
Date.valueOf("2012-10-14"));

myHomework.addProject(pg75Ex8);
. . .
System.out.println("The following assignment is due next:");
System.out.println(myHomework.getNextProject());
The assignment with the earliest due date is displayed but is not removed from the assignment log.

Java Class Library: The Class PriorityQueue
10.23

The standard package java.util in the Java Class Library contains the class PriorityQueue . This class
implements the interface Queue that we described earlier in this chapter. An instance of PriorityQueue
behaves like a priority queue, not a queue, in that its entries are ordered, with the entry having the smallest
value, and therefore the highest priority, at the front of the priority queue. Since PriorityQueue uses the
method compareTo to order its entries, the entries must belong to a class that implements the interface
Comparable . In addition, the entries cannot be null .
Here are the basic constructors and methods of the class PriorityQueue :

public PriorityQueue()
Creates an empty priority queue whose initial capacity is 11 entries.

public PriorityQueue( int initialCapacity)
Creates an empty priority queue having a given initial capacity.

public boolean add(T newEntry)
Adds a new entry to this priority queue, returning true if successful and throwing an excep-
tion if not.

public boolean offer(T newEntry)
Adds a new entry to this priority queue, returning true or false according to the success of
the operation.