org.apache.commons.collections.buffer

Class UnboundedFifoBuffer

public class UnboundedFifoBuffer extends AbstractCollection implements Buffer, 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 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: 405927 $ $Date: 2006-05-12 23:57:03 +0100 (Fri, 12 May 2006) $

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

Field Summary
protected Object[]buffer
The array of objects in the buffer.
protected inthead
The current head index.
protected inttail
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
booleanadd(Object obj)
Adds the given element to this buffer.
Objectget()
Returns the next object in the buffer.
booleanisEmpty()
Returns true if this buffer is empty; false otherwise.
Iteratoriterator()
Returns an iterator over this buffer's elements.
Objectremove()
Removes the next object from the buffer
intsize()
Returns the number of elements stored in the buffer.

Field Detail

buffer

protected transient 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: IllegalArgumentException if the size is less than 1

Method Detail

add

public boolean add(Object obj)
Adds the given element to this buffer.

Parameters: obj the element to add

Returns: true, always

Throws: NullPointerException if the given element is null

get

public Object get()
Returns the next object in the buffer.

Returns: the next object in the buffer

Throws: BufferUnderflowException if this buffer is empty

isEmpty

public boolean isEmpty()
Returns true if this buffer is empty; false otherwise.

Returns: true if this buffer is empty

iterator

public Iterator iterator()
Returns an iterator over this buffer's elements.

Returns: an iterator over this buffer's elements

remove

public Object remove()
Removes the next object from the buffer

Returns: the removed object

Throws: BufferUnderflowException if this buffer is empty

size

public int size()
Returns the number of elements stored in the buffer.

Returns: this buffer's size

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