Concurrent Set Queue

Question

Maybe this is a silly question, but I cannot seem to find an obvious answer.

I need a concurrent FIFO queue that contains only unique values. Attempting to add a val

Answer 1

A simple answer for a queue of unique objects can be as follow:

import java.util.concurrent.ConcurrentLinkedQueue;

public class FinalQueue {

    class Bin {
        private int a;
        private int b;

        public Bin(int a, int b) {
            this.a = a;
            this.b = b;
        }

        @Override
        public int hashCode() {
            return a * b;
        }

        public String toString() {
            return a + ":" + b;
        }

        @Override
        public boolean equals(Object obj) {
            if (this == obj)
                return true;
            if (obj == null)
                return false;
            if (getClass() != obj.getClass())
                return false;
            Bin other = (Bin) obj;
            if ((a != other.a) || (b != other.b))
                return false;
            return true;
        }
    }

    private ConcurrentLinkedQueue queue;

    public FinalQueue() {
        queue = new ConcurrentLinkedQueue();
    }

    public synchronized void enqueue(Bin ipAddress) {
        if (!queue.contains(ipAddress))
            queue.add(ipAddress);
    }

    public Bin dequeue() {
        return queue.poll();
    }

    public String toString() {
        return "" + queue;
    }

    /**
     * @param args
     */
    public static void main(String[] args) {
        FinalQueue queue = new FinalQueue();
        Bin a = queue.new Bin(2,6);

        queue.enqueue(a);
        queue.enqueue(queue.new Bin(13, 3));
        queue.enqueue(queue.new Bin(13, 3));
        queue.enqueue(queue.new Bin(14, 3));
        queue.enqueue(queue.new Bin(13, 9));
        queue.enqueue(queue.new Bin(18, 3));
        queue.enqueue(queue.new Bin(14, 7));
        Bin x= queue.dequeue();
        System.out.println(x.a);
        System.out.println(queue.toString());
        System.out.println("Dequeue..." + queue.dequeue());
        System.out.println("Dequeue..." + queue.dequeue());
        System.out.println(queue.toString());
    }
}