【Description】
A queue is a collection that implements the first-in-first-out protocal. This means that the only accessiable object in the collection in the first one that was inserted. The most common example of a queue is a waiting line.
【Interface】
In the java Collections Framework includes a queue interface, which is implemented by four classes: the linkedList class, the AbstractQueue class, the priorityQUeue class, and the ArrayDeque class. For simple FIFO queues, the arrayDeque class the best choice:
Queue<String> queue = new ArrayDeque<String>();
【Demo】
package com.albertshao.ds.queue;
// Data Structures with Java, Second Edition
// by John R. Hubbard
// Copyright 2007 by McGraw-Hill
import java.util.*;
public class TestStringQueue {
public static void main(String[] args) {
Queue<String> queue = new ArrayDeque<String>();
queue.add("GB");
queue.add("DE");
queue.add("FR");
queue.add("ES");
System.out.println(queue);
System.out.println("queue.element(): " + queue.element());
System.out.println("queue.remove(): " + queue.remove());
System.out.println(queue);
System.out.println("queue.remove(): " + queue.remove());
System.out.println(queue);
System.out.println("queue.add(\"IE\"): ");
queue.add("IE");
System.out.println(queue);
System.out.println("queue.remove(): " + queue.remove());
System.out.println(queue);
}
}
【Result】
[GB, DE, FR, ES]
queue.element(): GB
queue.remove(): GB
[DE, FR, ES]
queue.remove(): DE
[FR, ES]
queue.add("IE"):
[FR, ES, IE]
queue.remove(): FR
[ES, IE]