org.apache.commons.collections.buffer
Class UnboundedFifoBuffer

java.lang.Object
  java.util.AbstractCollection
      org.apache.commons.collections.buffer.UnboundedFifoBuffer

All Implemented Interfaces:

java.io.Serializable, java.lang.Iterable, java.util.Collection, Buffer

public class UnboundedFifoBuffer
extends java.util.AbstractCollection
implements Buffer, java.io.Serializable

UnboundedFifoBuffer is a very efficient implementation of Buffer that can grow to any size. 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 UnboundedFifoBuffer:

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

This buffer prevents null objects from being added.

This class is Serializable from Commons Collections 3.1.

Since:

Commons Collections 3.0 (previously in main package v2.1)

Version:

$Revision: 646777 $ $Date: 2008-04-10 13:33:15 +0100 (Thu, 10 Apr 2008) $

Author:

Avalon, Federico Barbieri, Berin Loritsch, Paul Jack, Stephen Colebourne, Andreas Schlosser, Thomas Knych, Jordan Krey

See Also:

Serialized Form

Field Summary

protected java.lang.Object[]	buffer The array of objects in the buffer.
protected int	head The current head index.
protected int	tail The current tail index.

Constructor Summary

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

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

Method Summary

boolean	add(java.lang.Object obj) Adds the given element to this buffer.
java.lang.Object	get() Returns the next object in the buffer.
boolean	isEmpty() Returns true if this buffer is empty; false otherwise.
java.util.Iterator	iterator() Returns an iterator over this buffer's elements.
java.lang.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

Methods inherited from interface java.util.Collection

addAll, clear, contains, containsAll, equals, hashCode, remove, removeAll, retainAll, toArray, toArray

Field Detail

buffer

protected transient java.lang.Object[] buffer

The array of objects in the buffer.

head

protected transient int head

The current head index.

tail

protected transient int tail

The current tail index.

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 initialSize)

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

Parameters:

initialSize - the initial size of the buffer

Throws:

java.lang.IllegalArgumentException - if the size is less than 1

Method Detail

size

public int size()

Returns the number of elements stored in the buffer.

Specified by:

size in interface java.util.Collection

Specified by:

size in class java.util.AbstractCollection

Returns:

this buffer's size

isEmpty

public boolean isEmpty()

Returns true if this buffer is empty; false otherwise.

Specified by:

isEmpty in interface java.util.Collection

Overrides:

isEmpty in class java.util.AbstractCollection

Returns:

true if this buffer is empty

add

public boolean add(java.lang.Object obj)

Adds the given element to this buffer.

Specified by:

add in interface java.util.Collection

Overrides:

add in class java.util.AbstractCollection

Parameters:

obj - the element to add

Returns:

true, always

Throws:

java.lang.NullPointerException - if the given element is null

get

public java.lang.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 java.lang.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 java.util.Iterator iterator()

Returns an iterator over this buffer's elements.

Specified by:

iterator in interface java.lang.Iterable

Specified by:

iterator in interface java.util.Collection

Specified by:

iterator in class java.util.AbstractCollection

Returns:

an iterator over this buffer's elements