Package org.apache.commons.collections.buffer

Class 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 14:33:15 +0200 (Thu, 10 Apr 2008) $
    See Also:
    Serialized Form

    • Field Summary

      Fields 
      Modifier and Type Field Description
      protected java.lang.Object[] buffer
      The array of objects in the buffer.
      protected int head
      The current head index.
      private static long serialVersionUID
      Serialization vesrion
      protected int tail
      The current tail index.

    • Constructor Summary

      Constructors 
      Constructor 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

      All Methods Instance Methods Concrete Methods 
      Modifier and Type Method Description
      boolean add​(java.lang.Object obj)
      Adds the given element to this buffer.
      private int decrement​(int index)
      Decrements the internal index.
      java.lang.Object get()
      Returns the next object in the buffer.
      private int increment​(int index)
      Increments the internal index.
      boolean isEmpty()
      Returns true if this buffer is empty; false otherwise.
      java.util.Iterator iterator()
      Returns an iterator over this buffer's elements.
      private void readObject​(java.io.ObjectInputStream in)
      Read the buffer in using a custom routine.
      java.lang.Object remove()
      Removes the next object from the buffer
      int size()
      Returns the number of elements stored in the buffer.
      private void writeObject​(java.io.ObjectOutputStream out)
      Write the buffer out using a custom routine.

      • 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, parallelStream, remove, removeAll, removeIf, retainAll, spliterator, stream, toArray, toArray, toArray

      • Methods inherited from interface java.lang.Iterable

        forEach

    • Field Detail

      • serialVersionUID

        private static final long serialVersionUID
        Serialization vesrion
        See Also:
        Constant Field Values

      • 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

      • writeObject

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

      • readObject

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

      • 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

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