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ActiveMQ example source code file (VMIndexLinkedList.java)

This example ActiveMQ source code file (VMIndexLinkedList.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

Java - ActiveMQ tags/keywords

cloneable, index, indexitem, indexitem, indexlinkedlist, indexoutofboundsexception, object, object, size, storeentry, storeentry, vmindexlinkedlist, vmindexlinkedlist

The ActiveMQ VMIndexLinkedList.java source code

/**
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You 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.activemq.kaha.impl.index;

import org.apache.activemq.kaha.StoreEntry;

/**
 * A linked list used by IndexItems
 * 
 * 
 */
public final class VMIndexLinkedList implements Cloneable, IndexLinkedList {
    private transient IndexItem root;
    private transient int size;

    /**
     * Constructs an empty list.
     * @param header 
     */
    public VMIndexLinkedList(IndexItem header) {
        this.root = header;
        this.root.next=this.root.prev=this.root;
    }
    
    public  void setRoot(IndexItem newRoot) {
        this.root=newRoot;
    }

    public synchronized IndexItem getRoot() {
        return root;
    }

    /*
     * (non-Javadoc)
     * 
     * @see org.apache.activemq.kaha.impl.IndexLinkedList#getFirst()
     */
    public synchronized IndexItem getFirst() {
        if (size == 0) {
            return null;
        }
        return root.next;
    }

    /*
     * (non-Javadoc)
     * 
     * @see org.apache.activemq.kaha.impl.IndexLinkedList#getLast()
     */
    public synchronized IndexItem getLast() {
        if (size == 0) {
            return null;
        }
        return root.prev;
    }

    /*
     * (non-Javadoc)
     * 
     * @see org.apache.activemq.kaha.impl.IndexLinkedList#removeFirst()
     */
    public synchronized StoreEntry removeFirst() {
        if (size == 0) {
            return null;
        }
        StoreEntry result = root.next;
        remove(root.next);
        return result;
    }

    /*
     * (non-Javadoc)
     * 
     * @see org.apache.activemq.kaha.impl.IndexLinkedList#removeLast()
     */
    public synchronized Object removeLast() {
        if (size == 0) {
            return null;
        }
        StoreEntry result = root.prev;
        remove(root.prev);
        return result;
    }

    /*
     * (non-Javadoc)
     * 
     * @see org.apache.activemq.kaha.impl.IndexLinkedList#addFirst(org.apache.activemq.kaha.impl.IndexItem)
     */
    public synchronized void addFirst(IndexItem item) {
        addBefore(item, root.next);
    }

    /*
     * (non-Javadoc)
     * 
     * @see org.apache.activemq.kaha.impl.IndexLinkedList#addLast(org.apache.activemq.kaha.impl.IndexItem)
     */
    public synchronized void addLast(IndexItem item) {
        addBefore(item, root);
    }

    /*
     * (non-Javadoc)
     * 
     * @see org.apache.activemq.kaha.impl.IndexLinkedList#size()
     */
    public synchronized int size() {
        return size;
    }

    /*
     * (non-Javadoc)
     * 
     * @see org.apache.activemq.kaha.impl.IndexLinkedList#isEmpty()
     */
    public synchronized boolean isEmpty() {
        return size == 0;
    }

    /*
     * (non-Javadoc)
     * 
     * @see org.apache.activemq.kaha.impl.IndexLinkedList#add(org.apache.activemq.kaha.impl.IndexItem)
     */
    public synchronized boolean add(IndexItem item) {
        addBefore(item, root);
        return true;
    }

    /*
     * (non-Javadoc)
     * 
     * @see org.apache.activemq.kaha.impl.IndexLinkedList#clear()
     */
    public synchronized void clear() {
        root.next=root.prev=root;
        size = 0;
    }

    // Positional Access Operations
    /*
     * (non-Javadoc)
     * 
     * @see org.apache.activemq.kaha.impl.IndexLinkedList#get(int)
     */
    public synchronized IndexItem get(int index) {
        return entry(index);
    }

    /*
     * (non-Javadoc)
     * 
     * @see org.apache.activemq.kaha.impl.IndexLinkedList#add(int,
     *      org.apache.activemq.kaha.impl.IndexItem)
     */
    public synchronized void add(int index, IndexItem element) {
        addBefore(element, index == size ? root : entry(index));
    }

    /*
     * (non-Javadoc)
     * 
     * @see org.apache.activemq.kaha.impl.IndexLinkedList#remove(int)
     */
    public synchronized Object remove(int index) {
        IndexItem e = entry(index);
        remove(e);
        return e;
    }

    /**
     * Return the indexed entry.
     */
    private IndexItem entry(int index) {
        if (index < 0 || index >= size) {
            throw new IndexOutOfBoundsException("Index: " + index + ", Size: " + size);
        }
        IndexItem e = root;
        if (index < size / 2) {
            for (int i = 0; i <= index; i++) {
                e = e.next;
            }
        } else {
            for (int i = size; i > index; i--) {
                e = e.prev;
            }
        }
        return e;
    }

    // Search Operations
    /*
     * (non-Javadoc)
     * 
     * @see org.apache.activemq.kaha.impl.IndexLinkedList#indexOf(org.apache.activemq.kaha.impl.IndexItem)
     */
    public synchronized int indexOf(StoreEntry o) {
        int index = 0;
        for (IndexItem e = root.next; e != root; e = e.next) {
            if (o == e) {
                return index;
            }
            index++;
        }
        return -1;
    }

    /*
     * (non-Javadoc)
     * 
     * @see org.apache.activemq.kaha.impl.IndexLinkedList#getNextEntry(org.apache.activemq.kaha.impl.IndexItem)
     */
    public synchronized IndexItem getNextEntry(IndexItem entry) {
        return entry.next != root ? entry.next : null;
    }

    /*
     * (non-Javadoc)
     * 
     * @see org.apache.activemq.kaha.impl.IndexLinkedList#getPrevEntry(org.apache.activemq.kaha.impl.IndexItem)
     */
    public synchronized IndexItem getPrevEntry(IndexItem entry) {
        return entry.prev != root ? entry.prev : null;
    }

    /*
     * (non-Javadoc)
     * 
     * @see org.apache.activemq.kaha.impl.IndexLinkedList#addBefore(org.apache.activemq.kaha.impl.IndexItem,
     *      org.apache.activemq.kaha.impl.IndexItem)
     */
    public synchronized void addBefore(IndexItem insert, IndexItem e) {
        insert.next = e;
        insert.prev = e.prev;
        insert.prev.next = insert;
        insert.next.prev = insert;
        size++;
    }

    /*
     * (non-Javadoc)
     * 
     * @see org.apache.activemq.kaha.impl.IndexLinkedList#remove(org.apache.activemq.kaha.impl.IndexItem)
     */
    public synchronized void remove(IndexItem e) {
        if (e == root || e.equals(root)) {
            return;
        }
        
        e.prev.next = e.next;
        e.next.prev = e.prev;
        size--;
    }

    /**
     * @return clone
     */
    public synchronized Object clone() {
        IndexLinkedList clone = new VMIndexLinkedList(this.root);
        for (IndexItem e = root.next; e != root; e = e.next) {
            clone.add(e);
        }
        return clone;
    }

    public synchronized StoreEntry getEntry(StoreEntry current) {
        return current;
    }

    /**
     * Update the indexes of a StoreEntry
     * 
     * @param current
     */
    public synchronized StoreEntry refreshEntry(StoreEntry current) {
        return current;
    }
}

Other ActiveMQ examples (source code examples)

Here is a short list of links related to this ActiveMQ VMIndexLinkedList.java source code file:

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