org.apache.commons.collections.buffer.CircularFifoBuffer.java Source code

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Here is the source code for org.apache.commons.collections.buffer.CircularFifoBuffer.java

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/*
 *  Copyright 2003-2004 The Apache Software Foundation
 *
 *  Licensed under the Apache License, Version 2.0 (the "License");
 *  you may not use this file except in compliance with the License.
 *  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 *  Unless required by applicable law or agreed to in writing, software
 *  distributed under the License is distributed on an "AS IS" BASIS,
 *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *  See the License for the specific language governing permissions and
 *  limitations under the License.
 */
package org.apache.commons.collections.buffer;

import java.util.Collection;

/** 
 * 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.
 * <p>
 * This class is Serializable from Commons Collections 3.1.
 * 
 * @since Commons Collections 3.0
 * @version $Revision: 1.5 $ $Date: 2004/06/03 22:02:13 $
 * 
 * @author Stefano Fornari
 * @author Stephen Colebourne
 */
public class CircularFifoBuffer extends BoundedFifoBuffer {

    /** Serialization version */
    private static final long serialVersionUID = -8423413834657610406L;

    /**
     * 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);
    }

}