Java Array Queues

Question

When creating 2 Queues like this:

    ArrayQueue q1 = new ArrayQueue();
    ArrayQueue q2 = new ArrayQueue();
    for (int i = 0; i < 5; i++) {
        q1.enqueue(new Integer(i));
    }
    for (int i = 5; i < 10; i++) {
        q2.enqueue(new Integer(i));
    }
    System.out.println("q1: " + q1);
    System.out.println("q2: " + q2);

It outputs: q1: 4,3,2,1,0 and q2: 9,8,7,6,5.

I need a method that merges Queue q2 into Queue q1 with interleaved elements. So if println'd again would output: q1: 0,5,1,6,2,7,3,8,4,9 and q2: 9,8,7,6,5.

My class contains all the appropriate methods enqueue, dequeue, peek, isEmpty, size, doubleSize... my method name is:

    public void mergedQs(ArrayQueue q) {
    }

Basically i want to add objects to two queues, then merge the second queue into the first(not just add them). Ideally i want to avoid casting them or using an ArrayList as i want them to remain Queues.

I would suggest you use the ConcurrentLikedDeque. Here is the API for it ConcurrentLinkedDeque. If you already have a class with methods like enqueue, dequeue etc, you can wrap the ConcurrentLinkedDeque into your class and use it as your main data structure for storing our objects. — nikkatsa
– nikkatsa, Commented Nov 22, 2012 at 12:45

Peter Lawrey · Accepted Answer · 2012-11-22 12:51:13Z

4

You might find this useful. It merges any number of queues.

public static <T> Queue<T> mergeQs(Queue<T> ... qs) {
    Queue<T> ret = new ConcurrentLinkedQueue<T>();
    boolean more;
    do {
        more = false;
        for (Queue<T> q : qs) 
            if (!q.isEmpty()) {
                ret.add(q.remove());
                more = true;
            }
    } while(more);
    return ret;
}

answered Nov 22, 2012 at 12:51

Peter Lawrey

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