PassportCheckpoint.java

package by.andd3dfx.common;

import java.util.ArrayDeque;
import java.util.LinkedList;
import java.util.Queue;

/**
 * <pre>
 * Implement a class Entry that will be used as a part of a larger simulation of a passport checkpoint.
 *
 * The class Entry needs to contain the following methods:
 * • void enter(String passportNumber) - puts the specified passport number at the end of the line.
 * • String exit() - removes the passport from the queue and returns the passport. If no passports are in the queue,
 * null should be returned.
 *
 * For example, the following code snippet should write "AB54321", "UK32032":
 *   Entry entry = new Entry();
 *   entry.enter("AB54321");
 *   entry.enter("UK32032");
 *
 *   System.out.println(entry.Exit());
 *   System.out.println(entry.Exit());
 * </pre>
 *
 * @see <a href="https://youtu.be/DAjin0U7NHA">Video solution</a>
 */
public class PassportCheckpoint {

    public static class Solution1 {
        private Queue<String> queue = new ArrayDeque<>();

        public void enter(String passportNumber) {
            queue.add(passportNumber);
        }

        public String exit() {
            return queue.poll();
        }
    }

    public static class Solution2 {
        private LinkedList<String> queue = new LinkedList<>();

        public void enter(String passportNumber) {
            queue.add(passportNumber);
        }

        public String exit() {
            return queue.poll();
        }
    }
}