com.xceptance.common.collection.LRUList Maven / Gradle / Ivy

Go to download

Show more of this group Show more artifacts with this name
Show all versions of xlt Show documentation

XLT (Xceptance LoadTest) is an extensive load and performance test tool developed and maintained by Xceptance.

The newest version!

/*
 * Copyright (c) 2005-2024 Xceptance Software Technologies GmbH
 *
 * 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 com.xceptance.common.collection;

import java.util.LinkedList;

/**
 * 
 * Linked list of fixed size supporting LRU-behavior. This is not a full implementation that overwrites all list
 * behavior. Only the methods add and get should be used when LRU-behavior including the size limit is needed.
 * 
 * 
 * All other methods are still available but their use will disturb the lru order and potentially violate the set size
 * limit.
 * 
 * 
 * @param 
 *            type of list elements
 * @author Hartmut Arlt (Xceptance Software Technologies GmbH)
 */
public class LRUList extends LinkedList
{
    /**
     * The serialVersionUID.
     */
    private static final long serialVersionUID = -6722448569778711452L;

    /**
     * Size of list.
     */
    private final int size;

    /**
     * Creates a new LRU list.
     * 
     * @param maxSize
     *            the maximum size of the list
     */
    public LRUList(final int maxSize)
    {
        super();
        this.size = maxSize;
    }

    /**
     * Adds the given element to the list.
     * 
     * If the maximum size of the list has been reached, the head of the list will be removed before the given element
     * will be added to the list.
     * 
     * 
     * @param element
     *            the element to add
     * @return true if the element was successfully added to the list, false otherwise
     */
    @Override
    public boolean add(final E element)
    {
        while (super.size() >= this.size)
        {
            super.poll();
        }

        return super.add(element);
    }

    /**
     * Gets the element at the given index.
     * 
     * To guarantee LRU behavior this element will be removed and added to the end of the list.
     * 
     * 
     * @param idx
     *            the index of the element to get
     * @return element at given index
     */
    @Override
    public E get(final int idx)
    {
        final E element = super.get(idx);

        super.remove(idx);
        super.add(element);

        return element;
    }
}