Khanh Queue

public class Queue {
    private String[] s = new String[1000];
    private int first = 0, last = -1;
    public boolean isEmpty(){
        return (first > last) ;
    }
    public void enqueue(String item){
        if (last == 1000) {
            System.out.println("Stackoverflow");
            return;
        }
        s[++last] = item;
    }
    public String dequeue(){
        if (isEmpty()) {
            System.out.println("Empty Stack");
            return null;
        }
        return s[first++];
    }
    public int size() {
        if (isEmpty()) return 0;
        return last - first + 1;
    }

    public static void main(String[] args){
        System.out.println("Chao cac ban");
        Queue q = new Queue();
        q.enqueue("chi");
        q.enqueue("anh");
        q.enqueue("moi");
        q.enqueue("biet");
        q.enqueue("chi");
        q.enqueue("anh");
        q.enqueue("moi");
        q.enqueue("hieu");
        q.enqueue("duoc");
        q.enqueue("em");

        while (!q.isEmpty()) {
            System.out.println("size = " + q.size());;
            System.out.println(q.dequeue());
        }
    }
}