import java.util.ArrayList;

public class ArrayListQueue {

    private ArrayList<Integer> queue;

    public ArrayListQueue() {
        queue = new ArrayList<Integer>();
    }

    public void enqueue(int key) {
        queue.add(key);
    }

    public int dequeue() {
        int removed = -1;
        if(!empty()) {
            removed = queue.get(0);
            queue.remove(0);
        }
        return removed;
    }

    public boolean empty() {
        return queue.isEmpty();
    }

    public void print() {
        System.out.println(queue);
    }

}


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import java.util.LinkedList;

public class LinkedListQueue {

    private LinkedList<Integer> queue;

    public LinkedListQueue() {
        queue = new LinkedList<Integer>();
    }

    public void enqueue(int key) {
        queue.add(key);
    }

    public int dequeue() {
        if(!empty()) {
            return queue.poll();
        }
        else {
            return -1;
        }
    }

    public boolean empty() {
        return queue.isEmpty();
    }

    public void print() {
        System.out.println(queue);
    }

}