com.sosnoski.util.queue
Class QueueBase

java.lang.Object
  |
  +--com.sosnoski.util.GrowableBase
        |
        +--com.sosnoski.util.queue.QueueBase

Direct Known Subclasses:

IntQueue, ObjectQueue, StringQueue

public abstract class QueueBase

extends GrowableBase

Base class for type-specific growable circular queue classes with any type of values (including primitive types). This class builds on the basic structure provided by GrowableBase, specializing it for usage as a queue. See the base class description for details of the implementation.

Queues based on this class are unsynchronized in order to provide the best possible performance for typical usage scenarios, so explicit synchronization must be implemented by the subclass or the application in cases where they are to be modified in a multithreaded environment.

Subclasses need to implement the abstract methods defined by the base class for working with the data array, as well as the actual data access methods (at least the basic add() and remove() methods).

Version:

1.0

Author:

Dennis M. Sosnoski

Field Summary

protected int	m_emptyOffset Offset for removing next item from queue.
protected int	m_fillOffset Offset for adding next item to queue.

Fields inherited from class com.sosnoski.util.GrowableBase

DEFAULT_SIZE, m_countLimit, m_maximumGrowth

Constructor Summary

QueueBase(int size, java.lang.Class type)
Constructor with partial specification.

QueueBase(int size, int growth, java.lang.Class type)
Constructor with full specification.

QueueBase(QueueBase base)
Copy (clone) constructor.

Method Summary

protected java.lang.Object	buildArray(java.lang.Class type) Constructs and returns a simple array containing the same data as held in this queue.
void	clear() Set the queue to the empty state.
void	discard(int count) Discard items from queue.
protected int	getAddIndex() Make space for adding a value to those in the queue.
protected int	getRemoveIndex() Removes the next item from the queue.
boolean	isEmpty() Check if queue is empty.
protected void	resizeCopy(java.lang.Object base, java.lang.Object grown) Copy data after array resize.
int	size() Get the number of values currently present in the queue.

Methods inherited from class com.sosnoski.util.GrowableBase

buildArray, discardValues, ensureCapacity, getArray, growArray, setArray

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

m_fillOffset

protected int m_fillOffset

Offset for adding next item to queue.

m_emptyOffset

protected int m_emptyOffset

Offset for removing next item from queue.

Constructor Detail

QueueBase

public QueueBase(int size,
                 int growth,
                 java.lang.Class type)

Constructor with full specification.

Parameters:

size - number of elements initially allowed in queue

growth - maximum size increment for growing queue

type - queue element type

QueueBase

public QueueBase(int size,
                 java.lang.Class type)

Constructor with partial specification.

Parameters:

size - number of elements initially allowed in queue

type - queue element type

QueueBase

public QueueBase(QueueBase base)

Copy (clone) constructor.

Parameters:

from - instance being copied

Method Detail

resizeCopy

protected void resizeCopy(java.lang.Object base,
                          java.lang.Object grown)

Copy data after array resize. This override of the default implementation rearranges the data present in the queue when the data was wrapped in the original array.

Overrides:

resizeCopy in class GrowableBase

Parameters:

base - original array containing data

grown - resized array for data

getAddIndex

protected int getAddIndex()

Make space for adding a value to those in the queue. If the underlying array is full, it is grown by the appropriate size increment so that the index value returned is always valid for the array in use by the time of the return.

Returns:

index position to store added element

getRemoveIndex

protected int getRemoveIndex()

Removes the next item from the queue.

Returns:

index position of removed element

Throws:

IllegalStateException - on attempt to remove an item from an empty queue

size

public int size()

Get the number of values currently present in the queue.

Returns:

count of values present

isEmpty

public boolean isEmpty()

Check if queue is empty.

Returns:

true if queue empty, false if not

clear

public void clear()

Set the queue to the empty state.

discard

public void discard(int count)

Discard items from queue.

Parameters:

count - number of items to be discarded

Throws:

IllegalStateException - if attempt to discard more items than present on queue

buildArray

protected java.lang.Object buildArray(java.lang.Class type)

Constructs and returns a simple array containing the same data as held in this queue.

Parameters:

type - element type for constructed array

Returns:

array containing a copy of the data