org.apache.commons.collections.buffer

## Class UnboundedFifoBuffer

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

- All Implemented Interfaces:
    Serializable, Iterable, Collection, Buffer

      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(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 14:33:15 +0200 (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

    Fields
    Modifier and Type | Field and Description
    --- | ---
    `protected 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

    Constructors
    Constructor and Description
    `UnboundedFifoBuffer()` Constructs an UnboundedFifoBuffer with the default number of elements.
    `UnboundedFifoBuffer(int initialSize)` Constructs an UnboundedFifoBuffer with the specified number of elements.

  - ### Method Summary

    Methods
    Modifier and Type | Method and Description
    --- | ---
    `boolean` | `add(Object obj)` 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`

    - ### Methods inherited from interface java.util.Collection

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

- - ### 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

    - #### size

          public int size()

      Returns the number of elements stored in the buffer.
      Specified by:
        `size` in interface `Collection`
      Specified by:
        `size` in class `AbstractCollection`
      Returns:
        this buffer's size

    - #### isEmpty

          public boolean isEmpty()

      Returns true if this buffer is empty; false otherwise.
      Specified by:
        `isEmpty` in interface `Collection`
      Overrides:
        `isEmpty` in class `AbstractCollection`
      Returns:
        true if this buffer is empty

    - #### add

          public boolean add(Object obj)

      Adds the given element to this buffer.
      Specified by:
        `add` in interface `Collection`
      Overrides:
        `add` in class `AbstractCollection`
      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.
      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.
      Specified by:
        `iterator` in interface `Iterable`
      Specified by:
        `iterator` in interface `Collection`
      Specified by:
        `iterator` in class `AbstractCollection`
      Returns:
        an iterator over this buffer's elements

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