public class SpecialQueue<ELEMENT> extends java.util.ArrayDeque<ELEMENT> {

    public SpecialQueue() {
        this(10);
    }

    public SpecialQueue(int capacity) {
        super(capacity);
    }

    public SpecialQueue<ELEMENT> join(SpecialQueue<ELEMENT> other) {
        SpecialQueue<ELEMENT> result =
                new SpecialQueue<ELEMENT>((this.size() + other.size()) * 2);

        ELEMENT[] data = (ELEMENT[]) this.toArray();
        for (ELEMENT e : data) {
            result.add(e);
        }

        data = (ELEMENT[]) other.toArray();
        for (ELEMENT e : data) {
            result.add(e);
        }

        return result;
    }

}