java队列的实现

队列也可以通过数组和链表两种方式来实现。

　1、链表方式实现

class Node{
    Node next = null;
    int data;
    public Node(int data){this.data = data;}
}

public class MyQueue<E>{
    private Node<E> head = null;
    private Node<E> tail = null;

    public boolean isEmpty(){
        return head == tail;
    }

    public void put(E data){
        Node<E> newNode = new Node<E>(data);
        if(head==null && tail==null){//队列为空
            head = newNode;
            tail = newNode;
        }
        else {
            tail.next = newNode;
            tail = newNode;
        }
    }

    public E pop(){
        if(this.isEmpty())
            return null;
        E data = head.data;
        head = head.next;
        return data;
    }

    public int size(){
        Node<E> tmp = head;
        int n = 0;
        while (tmp!=null) {
            n++;
            tmp = tmp.next;
        }
        return n;
    }
}

　2、list方式实现

public class MyQueue<E>{
    private Linkedlist<E> list = new Linkedlist<E>();
    private int size = 0;
    public synchronized void put(E e){
        list.addLast(e);
        size++;
    }

    public synchronized E pop(){
        size--;
        return list.removeFrist();
    }

    public synchronized boolean empty(){
        return size == 0;
    }

    public synchronized int size(){
        return size;
    }
}