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From scolebou...@apache.org
Subject cvs commit: jakarta-commons/collections/src/java/org/apache/commons/collections CircularFifoBuffer.java
Date Sat, 26 Apr 2003 15:10:56 GMT
scolebourne    2003/04/26 08:10:56

  Added:       collections/src/java/org/apache/commons/collections
                        CircularFifoBuffer.java
  Log:
  New buffer implementation that overwrites the oldest entry when full
  from Stefano Fornari
  
  Revision  Changes    Path
  1.1                  jakarta-commons/collections/src/java/org/apache/commons/collections/CircularFifoBuffer.java
  
  Index: CircularFifoBuffer.java
  ===================================================================
  /*
   * $Header: /home/cvs/jakarta-commons/collections/src/java/org/apache/commons/collections/CircularFifoBuffer.java,v
1.1 2003/04/26 15:10:56 scolebourne Exp $
   * ====================================================================
   *
   * The Apache Software License, Version 1.1
   *
   * Copyright (c) 2003 The Apache Software Foundation.  All rights
   * reserved.
   *
   * Redistribution and use in source and binary forms, with or without
   * modification, are permitted provided that the following conditions
   * are met:
   *
   * 1. Redistributions of source code must retain the above copyright
   *    notice, this list of conditions and the following disclaimer.
   *
   * 2. Redistributions in binary form must reproduce the above copyright
   *    notice, this list of conditions and the following disclaimer in
   *    the documentation and/or other materials provided with the
   *    distribution.
   *
   * 3. The end-user documentation included with the redistribution, if
   *    any, must include the following acknowlegement:
   *       "This product includes software developed by the
   *        Apache Software Foundation (http://www.apache.org/)."
   *    Alternately, this acknowlegement may appear in the software itself,
   *    if and wherever such third-party acknowlegements normally appear.
   *
   * 4. The names "The Jakarta Project", "Commons", and "Apache Software
   *    Foundation" must not be used to endorse or promote products derived
   *    from this software without prior written permission. For written
   *    permission, please contact apache@apache.org.
   *
   * 5. Products derived from this software may not be called "Apache"
   *    nor may "Apache" appear in their names without prior written
   *    permission of the Apache Group.
   *
   * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
   * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
   * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
   * DISCLAIMED.  IN NO EVENT SHALL THE APACHE SOFTWARE FOUNDATION OR
   * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
   * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
   * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
   * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
   * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
   * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
   * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   * SUCH DAMAGE.
   * ====================================================================
   *
   * This software consists of voluntary contributions made by many
   * individuals on behalf of the Apache Software Foundation.  For more
   * information on the Apache Software Foundation, please see
   * <http://www.apache.org/>.
   *
   */
  package org.apache.commons.collections;
  
  import java.util.Collection;
  
  import org.apache.commons.collections.BoundedFifoBuffer;
  
  /** 
   * CircularFifoBuffer is a first in first out buffer with a fixed size that
   * replaces its oldest element if full.
   * <p>
   * The removal order of a <code>CircularFifoBuffer</code> 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.
   * <p>
   * The {@link #add(Object)}, {@link #remove()} and {@link #get()} operations
   * all perform in constant time.  All other operations perform in linear
   * time or worse.
   * <p>
   * Note that this implementation is not synchronized.  The following can be
   * used to provide synchronized access to your <code>CircularFifoBuffer</code>:
   * <pre>
   *   Buffer fifo = BufferUtils.synchronizedBuffer(new CircularFifoBuffer());
   * </pre>
   * <p>
   * This buffer prevents null objects from being added.
   * 
   * @since Commons Collections 2.2
   * @version $Revision: 1.1 $ $Date: 2003/04/26 15:10:56 $
   * 
   * @author Stefano Fornari
   * @author Stephen Colebourne
   */
  public class CircularFifoBuffer extends BoundedFifoBuffer {
  
      /**
       * Constructor that creates a buffer with the default size of 32.
       */
      public CircularFifoBuffer() {
          super(32);
      }
  
      /**
       * Constructor that creates a buffer with the specified size.
       * 
       * @param size  the size of the buffer (cannot be changed)
       * @throws IllegalArgumentException  if the size is less than 1
       */
      public CircularFifoBuffer(int size) {
          super(size);
      }
  
      /**
       * Constructor that creates a buffer from the specified collection.
       * The collection size also sets the buffer size
       * 
       * @param coll  the collection to copy into the buffer, may not be null
       * @throws NullPointerException if the collection is null
       */
      public CircularFifoBuffer(Collection coll) {
          super(coll);
      }
  
      /**
       * If the buffer is full, the least recently added element is discarded so
       * that a new element can be inserted.
       *
       * @param element the element to add
       * @return true, always
       */
      public boolean add(Object element) {
          if (isFull()) {
              remove();
          }
          return super.add(element);
      }
      
  }
  
  
  

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