java队列queue队列大小_java实现简单队列queue「建议收藏」

java队列queue队列大小_java实现简单队列queue「建议收藏」1.队列的特点队列是一种比较特殊的线性结构

java队列queue队列大小_java实现简单队列queue「建议收藏」"

项目github地址:bitcarmanlee easy-algorithm-interview-and-practice
欢迎大家star,留言,一起学习进步

1.队列的特点

队列是一种比较特殊的线性结构。它只允许在表的前端(front)进行删除操作,而在表的后端(rear)进行插入操作。进行插入操作的端称为队尾,进行删除操作的端称为队头。
队列中最先插入的元素也将最先被删除,对应的最后插入的元素将最后被删除。因此队列又称为“先进先出”(FIFO—first in first out)的线性表,与栈(FILO-first in last out)刚好相反。

2.java中的队列

java中的Queue接口就实现了队列的功能。

public interface Queue<E> extends Collection<E> {
    /**
     * Inserts the specified element into this queue if it is possible to do so
     * immediately without violating capacity restrictions, returning
     * {@code true} upon success and throwing an {@code IllegalStateException}
     * if no space is currently available.
     *
     * @param e the element to add
     * @return {@code true} (as specified by {@link Collection#add})
     * @throws IllegalStateException if the element cannot be added at this
     *         time due to capacity restrictions
     * @throws ClassCastException if the class of the specified element
     *         prevents it from being added to this queue
     * @throws NullPointerException if the specified element is null and
     *         this queue does not permit null elements
     * @throws IllegalArgumentException if some property of this element
     *         prevents it from being added to this queue
     */
    boolean add(E e);

    /**
     * Inserts the specified element into this queue if it is possible to do
     * so immediately without violating capacity restrictions.
     * When using a capacity-restricted queue, this method is generally
     * preferable to {@link #add}, which can fail to insert an element only
     * by throwing an exception.
     *
     * @param e the element to add
     * @return {@code true} if the element was added to this queue, else
     *         {@code false}
     * @throws ClassCastException if the class of the specified element
     *         prevents it from being added to this queue
     * @throws NullPointerException if the specified element is null and
     *         this queue does not permit null elements
     * @throws IllegalArgumentException if some property of this element
     *         prevents it from being added to this queue
     */
    boolean offer(E e);

    /**
     * Retrieves and removes the head of this queue.  This method differs
     * from {@link #poll poll} only in that it throws an exception if this
     * queue is empty.
     *
     * @return the head of this queue
     * @throws NoSuchElementException if this queue is empty
     */
    E remove();

    /**
     * Retrieves and removes the head of this queue,
     * or returns {@code null} if this queue is empty.
     *
     * @return the head of this queue, or {@code null} if this queue is empty
     */
    E poll();

    /**
     * Retrieves, but does not remove, the head of this queue.  This method
     * differs from {@link #peek peek} only in that it throws an exception
     * if this queue is empty.
     *
     * @return the head of this queue
     * @throws NoSuchElementException if this queue is empty
     */
    E element();

    /**
     * Retrieves, but does not remove, the head of this queue,
     * or returns {@code null} if this queue is empty.
     *
     * @return the head of this queue, or {@code null} if this queue is empty
     */
    E peek();
}

不得不说,JDK里的代码以及注释看着就是很舒服。各位稍微花点时间看看JDK里的源码以及注释,相信会有很多收获。

3.测试Queue接口

JDK中,LinkedList类实现了Queue接口,可以当Queue使用。

public class QueueTest {

    @Test
    public void test() {
        Queue<Integer> queue = new LinkedList<>();
        queue.offer(1);
        queue.offer(2);
        queue.offer(3);
        queue.offer(4);
        for(int e : queue) {
            System.out.println(e);
        }
        System.out.println("----------");
        System.out.println("poll : " + queue.poll());
        System.out.println("----------");

        for(int e : queue) {
            System.out.println(e);
        }
        System.out.println("ele is: " + queue.element());
        System.out.println("----------");

        for(int e : queue) {
            System.out.println(e);
        }

        System.out.println("peek : " + queue.peek());
        System.out.println("----------");

        for(int e : queue) {
            System.out.println(e);
        }
    }
}

最终代码运行的结果:

1
2
3
4
----------
poll : 1
----------
2
3
4
ele is: 2
----------
2
3
4
peek : 2
----------
2
3
4

结合第二部分内容,可以有以下结论:
1.尽量使用offer()方法添加元素,使用poll()方法移除元素。dd()和remove()方法在失败的时候会抛出异常。
2.peek方法不会删除元素, Retrieves, but does not remove, the head of this queue,

今天的文章java队列queue队列大小_java实现简单队列queue「建议收藏」分享到此就结束了,感谢您的阅读。

版权声明:本文内容由互联网用户自发贡献,该文观点仅代表作者本人。本站仅提供信息存储空间服务,不拥有所有权,不承担相关法律责任。如发现本站有涉嫌侵权/违法违规的内容, 请发送邮件至 举报,一经查实,本站将立刻删除。
如需转载请保留出处:https://bianchenghao.cn/70299.html

(0)
编程小号编程小号

相关推荐

发表回复

您的电子邮箱地址不会被公开。 必填项已用*标注