每日一省————链表之队列的简单实现-优快云博客

本文链接：https://blog.youkuaiyun.com/nmgrd/article/details/52205507

本文介绍了一个简单的队列数据结构实现，并且该队列同时实现了Iterable接口。通过具体代码示例展示了队列的基本操作如入队、出队等，并提供了一个完整的运行示例。

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这是一个队列的简单实现，同时也实现了Iterable接口。代码较简单，比起JDK自带的队列实现，简直弱爆了。但本人主要是为了复习数据结构而已，个人觉得还是有一定参考价值的，有兴趣的看一看吧。

具体实现代码如下：



import java.util.Iterator;
import java.util.NoSuchElementException;

public class Queue<T> implements Iterable<T> {

    private Node<T> first;
    private Node<T> last;
    private int size;

    private static class Node<T> {
        private T item;
        private Node<T> next;
    }

    public Queue() {
        first = null;
        last = null;
        size = 0;
    }

    public boolean isEmpty() {
        return first == null;
    }

    public void enqueue(T t) {
        Node<T> oldLast = last;
        last = new Node<T>();
        last.item = t;
        last.next = null;
        if (isEmpty()) {
            first = last;
        } else {
            oldLast.next = last;
        }
        size++;

    }

    public T dequeue() {
        if (isEmpty())
            throw new NoSuchElementException("队列为空");
        T item = first.item;
        first = first.next;
        size--;
        if (isEmpty())
            last = null;
        return item;
    }

    public T peek() {
        if (isEmpty())
            throw new NoSuchElementException("队列为空");
        return first.item;
    }

    public int size() {
        return size;
    }

    @Override
    public Iterator<T> iterator() {
        return new QueueIterator<T>(first);
    }

    /**
     * 队列的迭代器实现
     */
    private class QueueIterator<T> implements Iterator<T> {

        private Node<T> current;

        public QueueIterator(Node<T> current) {
            this.current = current;
        }

        @Override
        public boolean hasNext() {
            return current != null;
        }

        public void remove() {
            throw new UnsupportedOperationException();
        }

        @Override
        public T next() {
            if (!hasNext())
                throw new NoSuchElementException();
            T item = current.item;
            current = current.next;
            return item;
        }

    }

    public String toString() {
        StringBuilder s = new StringBuilder();
        for (T item : this)
            s.append(item + " -> ");
        return s.toString() + null;
    }

    public static void main(String... args) {
        Queue<String> queue = new Queue<String>();
        queue.enqueue("I");
        queue.enqueue("am");
        queue.enqueue("a");
        queue.enqueue("hero");
        System.out.println(queue);
        System.out.println("队列的大小是" + queue.size);

        Iterator<String> iterator = queue.iterator();
        iterator.forEachRemaining(t -> System.out.println("[ " + t + "]"));

        queue.dequeue();
        System.out.println(queue);
        System.out.println("队列的大小是" + queue.size);

        queue.dequeue();
        System.out.println(queue);
        System.out.println("队列的大小是" + queue.size);

        queue.dequeue();
        System.out.println(queue);
        System.out.println("队列的大小是" + queue.size);

        queue.dequeue();
        System.out.println(queue);
        System.out.println("队列的大小是" + queue.size);

        queue.dequeue();
        System.out.println(queue);
        System.out.println("队列的大小是" + queue.size);

    }

}