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) $
See Also:
  • Field Details

    • serialVersionUID

      private static final long serialVersionUID
      Serialization vesrion
      See Also:
    • buffer

      protected transient Object[] buffer
      The array of objects in the buffer.
    • tail

      protected transient int tail
      The current tail index.
  • Constructor Details

    • 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 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
    • 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
    • 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