Package org.apache.commons.collections.buffer

Class BoundedFifoBuffer

java.lang.Object
java.util.AbstractCollection
org.apache.commons.collections.buffer.BoundedFifoBuffer
All Implemented Interfaces:
Serializable, Iterable, Collection, BoundedCollection, Buffer
Direct Known Subclasses:
CircularFifoBuffer
public class BoundedFifoBuffer extends AbstractCollection implements Buffer, BoundedCollection, Serializable
The BoundedFifoBuffer is a very efficient implementation of Buffer that is of a fixed size.

The removal order of a BoundedFifoBuffer 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 add(Object), remove() and get() operations all perform in 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 BoundedFifoBuffer: 

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

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) $
See Also:

  • Field Details

    • serialVersionUID

      private static final long serialVersionUID
      Serialization version
      See Also:

    • elements

      private transient Object[] elements
      Underlying storage array

    • start

      private transient int start
      Array index of first (oldest) buffer element

    • end

      private transient int end
      Index mod maxElements of the array position following the last buffer element. Buffer elements start at elements[start] and "wrap around" elements[maxElements-1], ending at elements[decrement(end)]. For example, elements = {c,a,b}, start=1, end=1 corresponds to the buffer [a,b,c].

    • full

      private transient boolean full
      Flag to indicate if the buffer is currently full.

    • maxElements

      private final int maxElements
      Capacity of the buffer

  • Constructor Details

    • BoundedFifoBuffer

      public BoundedFifoBuffer()
      Constructs a new BoundedFifoBuffer big enough to hold 32 elements.

    • BoundedFifoBuffer

      public BoundedFifoBuffer(int size)
      Constructs a new BoundedFifoBuffer big enough to hold the specified number of elements.
      Parameters:
      size - the maximum number of elements for this fifo
      Throws:
      IllegalArgumentException - if the size is less than 1

    • BoundedFifoBuffer

      public BoundedFifoBuffer(Collection coll)
      Constructs a new BoundedFifoBuffer big enough to hold all of the elements in the specified collection. That collection's elements will also be added to the buffer.
      Parameters:
      coll - the collection whose elements to add, may not be null
      Throws:
      NullPointerException - if the collection is null

  • Method Details

    • writeObject

      private void writeObject(ObjectOutputStream out) throws IOException
      Write the buffer out using a custom routine.
      Parameters:
      out - the output stream
      Throws:
      IOException

    • readObject

      private void readObject(ObjectInputStream in) throws IOException, ClassNotFoundException
      Read the buffer in using a custom routine.
      Parameters:
      in - the input stream
      Throws:
      IOException
      ClassNotFoundException

    • 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

    • isFull

      public boolean isFull()
      Returns true if this collection is full and no new elements can be added.
      Specified by:
      isFull in interface BoundedCollection
      Returns:
      true if the collection is full

    • maxSize

      public int maxSize()
      Gets the maximum size of the collection (the bound).
      Specified by:
      maxSize in interface BoundedCollection
      Returns:
      the maximum number of elements the collection can hold

    • clear

      public void clear()
      Clears this buffer.
      Specified by:
      clear in interface Collection
      Overrides:
      clear in class AbstractCollection

    • add

      public boolean add(Object element)
      Adds the given element to this buffer.
      Specified by:
      add in interface Collection
      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 least recently inserted element in this buffer.
      Specified by:
      get in interface Buffer
      Returns:
      the least recently inserted element
      Throws:
      BufferUnderflowException - if the buffer is empty

    • remove

      public Object remove()
      Removes the least recently inserted element from this buffer.
      Specified by:
      remove in interface Buffer
      Returns:
      the least recently inserted element
      Throws:
      BufferUnderflowException - if the buffer is empty

    • increment

      private int increment(int index)
      Increments the internal index.
      Parameters:
      index - the index to increment
      Returns:
      the updated index

    • decrement

      private int decrement(int index)
      Decrements the internal index.
      Parameters:
      index - the index to decrement
      Returns:
      the updated index

    • iterator

      public Iterator iterator()
      Returns an iterator over this buffer's elements.
      Specified by:
      iterator in interface Collection
      Specified by:
      iterator in interface Iterable
      Specified by:
      iterator in class AbstractCollection
      Returns:
      an iterator over this buffer's elements