Interface UpdatablePriorityQueue<T,P extends java.lang.Comparable<? super P>>

Type Parameters:

T - the type of the items stored in the queue.

P - the type of the priority of each item.

All Superinterfaces:

PriorityQueue<PriorityPair<T,P>>

public interface UpdatablePriorityQueue<T,P extends java.lang.Comparable<? super P>>
extends PriorityQueue<PriorityPair<T,P>>

An interface for the Updatable Priority Queue ADT, which allows the user to query and change the priority of items in the queue. Each implementation of this interface shall define a special "sentinel" priority value that indicates an item is not in the queue. Setting an item's priority to this value in fact removes it from the queue. Removing a non-member item is a no-op. In addition, adding an item may be accomplished, from the user side, simply by setting its priority to a non-sentinel value.

Method Summary

P	getPriority(T item) Returns the priority of the given item, or, if that item is not in the queue, an implementation-specific sentinel value.
P	nonMemberPriority() Returns the sentinel value used by getPriority() to indicate items not currently stored in the queue.
boolean	setPriority(T item, P newPriority) Sets the priority of a given item.

Methods inherited from interface PriorityQueue

add, clear, isEmpty, peek, remove

Method Detail

setPriority

boolean setPriority(T item,
                    P newPriority)

Sets the priority of a given item. The consequences of this operation vary depending on two conditions: OLD: the item is already in the queue. DEL: "newPriority" is the non-member priority sentinel value. The four cases covered by combinations of these conditions are: 1. If OLD and !DEL, this method changes the item's priority. 2. If !OLD and !DEL, this method adds the item. 3. If OLD and DEL, this method removes the item. 4. If !OLD and DEL, this method is a no-op (removing a non-member). The return value is !DEL (true in cases 1 and 2; false in 3 and 4).

Returns:

true if the pair (item, newPriority) is in the queue after the call.

nonMemberPriority

P nonMemberPriority()

Returns the sentinel value used by getPriority() to indicate items not currently stored in the queue.

getPriority

P getPriority(T item)

Returns the priority of the given item, or, if that item is not in the queue, an implementation-specific sentinel value.