import java.util.*;

public class AntreanLayanan {
    public static void main(String[] args) {
        Queue<String> antrean = new ArrayDeque<>();
        antrean.offer("Budi");
        antrean.offer("Siti");
        antrean.offer("Dewi");
        System.out.println("Isi antrean : " + antrean);

        // peek() melihat kepala antrean tanpa menghapus.
        System.out.println("peek()      : " + antrean.peek());
        System.out.println("Setelah peek: " + antrean);

        // poll() mengambil kepala antrean dan menghapusnya (FIFO).
        System.out.println("poll()      : " + antrean.poll());
        System.out.println("poll()      : " + antrean.poll());
        System.out.println("Sisa        : " + antrean);

        // Antrean sudah kosong: bentuk nilai khusus mengembalikan penanda.
        System.out.println("poll() lagi : " + antrean.poll());
        System.out.println("peek() lagi : " + antrean.peek());
        System.out.println("isEmpty()   : " + antrean.isEmpty());
    }
}