数组实现队列

权当个人笔记

package com.zyw.collection.queue;
/**
 * target:using array to realize Bi-directional circulation Queue.
 * first-in-first-out
 * @author KeepGoingPawn
 * @date 2018.06.25
 */
public class Queue {
    private int[] space = null;//the space of queue.
    private int head = 0;//the head index of queue.
    private int tail = 0;//the tail index of queue.
    private int maxLength = 0;//the max length of queue.

    /**
     * The constructor method of having params.
     * @param length
     */
    public Queue(int length){
        this.maxLength = length;
        space = new int[length];
    }

    /**
     * The realize of push's method
     */
    public void push(int x){
        if(isFull()){
            System.out.println("The queue is full.");
        }
        space[tail] = x;
        tail = (tail+1) % maxLength;
    }

    /**
     * the realize of pop's method
     */
    public void pop(){
        if(isEmpty()){
            System.out.println("The queue is empty.");
        }
        head = (head+1) % maxLength;
    }

    /**
     * watch the head element
     * @return
     */
    public int front(){
        return space[head];
    }

    /**
     * watch the tail element
     * @return
     */
    public int back(){
        return space[(tail+maxLength-1) % maxLength];
    }

    /**
     * watch the total num of the queue.
     * @return
     */
    public int size(){
        return (tail +maxLength-head) % maxLength;
    }

    /**
     * judge the queue is empty or not.
     * @return
     */
    public boolean isEmpty(){
        if(tail == head){
            return true;
        }
        return false;
    }

    /**
     * judge the queue is full or not.
     * @return
     */
    public boolean isFull(){
        //If the tail's next index is head,indicates that the queue is full.
        if((tail+1) % maxLength == head){
            return true;
        }
        return false;
    }

    public static void main(String[] args) {
        Queue q = new Queue(5);
        q.push(1);
        q.push(2);
        q.push(3);
        q.push(4);
        System.out.println("front's element:"+q.front()+" tail's element:"+q.back()+" the total's num:"+q.size());
        q.push(4);
        q.push(5);
        q.push(6);
        q.pop();
        q.pop();
        q.push(7);
        System.out.println("front's element:"+q.front()+" tail's element:"+q.back()+" the total's num:"+q.size());
    }
}