Java Component Examples

LockFreeEBDeque Example

/*
* Copyright (c) 2008 IBM Corporation
*
* 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.amino.examples;

/*   The Deque is a double-ended queue, elements can only be added to
*   or removed from the front (head) or back (tail).
*   This example shows the mainly interfaces of EBDeque which adds
*   elimination mechanism to deal with high contention rate scenario.
*   Including : element(), offer(), peek(), poll(), iterator(),
*               getFirst(), getLast(), add(), clear(), removeFist(), removeLast()
*
*   The DequeAdder class will add items of String from "1" to "ELEMENT_NUM".
*   The DequeRemover class will remove no more than ELEMENT_NUM items.
*   The main thread will wait for all the threads in pool to finish.
*   2009/05/22
*/

import java.util.Deque;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.TimeUnit;
import java.util.Iterator;

import org.amino.ds.lockfree.EBDeque;

public class EBDequeExample {

    public static final int ELEMENT_NUM = 100;
    private static final int TASKS_NUM = 4;
    public static void main(String[] argvs) {

        ExecutorService exec = Executors.newFixedThreadPool(TASKS_NUM);

        final EBDeque<String> dequeStr = new EBDeque<String>();

        for (int i = 0; i < TASKS_NUM; ++i) {
            exec.submit(new DequeAdder(dequeStr));
            if (i%2 == 0)exec.submit(new DequeRemover(dequeStr));
        }

        exec.shutdown();

        // Wait until all the threads in pool to finish.
        try {
            while(!exec.awaitTermination(600, TimeUnit.SECONDS));
        } catch (InterruptedException e) {
            e.printStackTrace();
        }

        // If the Deque is empty now, the program will exit.
        if (dequeStr.isEmpty())
        {
            System.out.println("The Deque is empty, so I will exit!");
            System.exit(1);
        }

        String first = dequeStr.poll();
        dequeStr.addFirst(first);

        String first1 = dequeStr.removeFirst();
        assert(first == first1);

        // The offer*() has the same functionality as add*().
        dequeStr.offerLast(first1);
        String last = dequeStr.peekLast();
        String last1 = dequeStr.getLast();
        String last2 = dequeStr.pollLast();
        assert(last == last1 && last1 == last2 && first1 == last);

        dequeStr.addLast(first1);
        last = dequeStr.peekLast();
        last1 = dequeStr.getLast();
        last2 = dequeStr.pollLast();
        assert(last == last1 && last1 == last2 && first1 == last);


        // Print all the elements in Deque.
        for (String str : dequeStr)
            System.out.println(str);

        System.out.println("Deque size before clearing: "+ dequeStr.size());
        dequeStr.clear();
        System.out.println("Deque size after clearing: "+ dequeStr.size());
    }
}

/*
*  The DequeAdder class will add elements to the given Deque.
*/
class DequeAdder implements Runnable {
    Deque<String> taskDq;
    private int count = 0;

    public DequeAdder(EBDeque<String> taskDeque)
    {
        taskDq = taskDeque;
    }

    public void run(){
        while (count < EBDequeExample.ELEMENT_NUM)
        {
            // The add* functions have no return value.
            taskDq.addFirst(Integer.toString(count++));
            taskDq.addLast(Integer.toString(count));
            System.out.println(Thread.currentThread()+ " Added first and last:" + count);

            // The offer* functions have boolean return value.
            if (!taskDq.offerFirst(Integer.toString(count++)))
                System.out.println("offerFirst() failed!");
            if (!taskDq.offerLast(Integer.toString(count)))
                System.out.println("offerFirst() failed!");
            System.out.println(Thread.currentThread()+ " Offered first and last:" + count);
        }
        Thread.yield();
    }
}

/*
*  The DequeRemover class will remove the existed elements from the given Deque.
*/
class DequeRemover implements Runnable {
    Deque<String> taskDq;

    public DequeRemover(EBDeque<String> taskDeque)
    {
        taskDq = taskDeque;
    }

    public void run(){
        int times = 0;

        while (times < EBDequeExample.ELEMENT_NUM)
        {
            String toRemoveFirst = taskDq.removeFirst();
            String toRemoveLast = taskDq.removeLast();
            System.out.println(Thread.currentThread()+ " Removed first: " + toRemoveFirst);
            System.out.println(Thread.currentThread()+ " Removed last: " + toRemoveLast);
            times++;
        }
        Thread.yield();
    }
}
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