org.apache.commons.collections
Class UnboundedFifoBuffer

java.lang.Object
  |
  +--java.util.AbstractCollection
        |
        +--org.apache.commons.collections.UnboundedFifoBuffer

public final class UnboundedFifoBuffer

extends AbstractCollection

implements Buffer

UnboundedFifoBuffer is a very efficient buffer implementation. According to performance testing, it exhibits a constant access time, but it also outperforms ArrayList when used for the same purpose.

The removal order of an UnboundedFifoBuffer is based on the insertion order; elements are removed in the same order in which they were added. The iteration order is the same as the removal order.

The remove() and get() operations perform in constant time. The add(Object) operation performs in amortized constant time. All other operations perform in linear time or worse.

Note that this implementation is not synchronized. The following can be used to provide synchronized access to your UnboundedFifo:

   Buffer fifo = BufferUtils.synchronizedBuffer(new UnboundedFifo());
 

This buffer prevents null objects from being added.

Since:

2.1

Version:

$Id: UnboundedFifoBuffer.java,v 1.5 2002/10/13 12:59:04 scolebourne Exp $

Author:

Avalon, Federico Barbieri, Berin Loritsch, Paul Jack, Stephen Colebourne

Field Summary

protected Object[]	m_buffer
protected int	m_head
protected int	m_tail

Constructor Summary

UnboundedFifoBuffer()
Constructs an UnboundedFifoBuffer with the default number of elements.

UnboundedFifoBuffer(int size)
Constructs an UnboundedFifoBuffer with the specified number of elements.

Method Summary

boolean	add(Object o) Adds the given element to this buffer.
Object	get() Returns the next object in the buffer.
boolean	isEmpty() Returns true if this buffer is empty; false otherwise.
Iterator	iterator() Returns an iterator over this buffer's elements.
Object	remove() Removes the next object from the buffer
int	size() Returns the number of elements stored in the buffer.

Methods inherited from class java.util.AbstractCollection

addAll, clear, contains, containsAll, remove, removeAll, retainAll, toArray, toArray, toString

Methods inherited from class java.lang.Object

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

Field Detail

m_buffer

protected Object[] m_buffer

m_head

protected int m_head

m_tail

protected int m_tail

Constructor Detail

UnboundedFifoBuffer

public UnboundedFifoBuffer()

Constructs an UnboundedFifoBuffer with the default number of elements. It is exactly the same as performing the following:

   new UnboundedFifoBuffer(32);
 

UnboundedFifoBuffer

public UnboundedFifoBuffer(int size)

Constructs an UnboundedFifoBuffer with the specified number of elements. The integer must be a positive integer.

Throws:

IllegalArgumentException - if the size is less than 1

Method Detail

size

public int size()

Returns the number of elements stored in the buffer.

Overrides:

size in class AbstractCollection

Returns:

this buffer's size

isEmpty

public boolean isEmpty()

Returns true if this buffer is empty; false otherwise.

Overrides:

isEmpty in class AbstractCollection

Returns:

true if this buffer is empty

add

public boolean add(Object o)

Adds the given element to this buffer.

Overrides:

add in class AbstractCollection

Parameters:

element - the element to add

Returns:

true, always

Throws:

NullPointerException - if the given element is null

BufferOverflowException - if this buffer is full

get

public Object get()

Returns the next object in the buffer.

Specified by:

get in interface Buffer

Returns:

the next object in the buffer

Throws:

BufferUnderflowException - if this buffer is empty

remove

public Object remove()

Removes the next object from the buffer

Specified by:

remove in interface Buffer

Returns:

the removed object

Throws:

BufferUnderflowException - if this buffer is empty

iterator

public Iterator iterator()

Returns an iterator over this buffer's elements.

Overrides:

iterator in class AbstractCollection

Returns:

an iterator over this buffer's elements