队列结构的实现

public class ArrayQueue {

    private int maxsize=16;
    private int last;
    private int front;
    private int[] arr;

    public ArrayQueue(int maxsize) {
        if(maxsize<=0){
            throw new RuntimeException("长度需要大于0");
        }
        this.maxsize = maxsize;
        arr=new int[maxsize];
        this.last=-1;
        this.front=-1;
    }
    private void push(int value){
        //先判断队列是否已满
        if(this.isFull()){
            throw new RuntimeException("队列已满");
        }
        if(last==maxsize-1){
            //已经是最后一个索引了
            int[] newArr=new int[maxsize];
            int j=0;
            for(int k=front+1;k<=last;k++){
                newArr[j]=arr[k];
                j++;
            }
            last=last-front-1;
            front=-1;
            arr=newArr;
        }
        last++;
        arr[last]=value;

    }
    private boolean isFull(){
        if(front==-1){
            return this.last==maxsize-1;
        }
        return this.last-this.front==maxsize-1;
    }

    private boolean isEmpty(){
        return front>=last;
    }

    public int pop(){
        if(this.isEmpty()){
            throw new RuntimeException("队列没有数据");
        }
        front++;
        int k=arr[front];
        return k;
    }
    public int peek(){
        if(isEmpty()){
            throw new RuntimeException("队列没有数据");
        }
        int value=arr[front+1];
        return value;
    }

    public void printIndex(String prefix){
        System.out.println(prefix);
        System.out.println("last:"+last);
        System.out.println("front:"+front);
    }

    public static void main(String[] args) {
        ArrayQueue queue = new ArrayQueue(3);
        queue.push(1);
        queue.push(3);
        queue.push(9);
        System.out.println(queue.pop());
        System.out.println(queue.pop());
        System.out.println(queue.pop());
        queue.push(8);
        queue.push(8);
        queue.push(6);
        System.out.println(queue.pop());
        System.out.println(queue.pop());
        queue.push(8);
        System.out.println(queue.pop());

    }




}

第二种是循环数组来实现

package com.yang.xiao.hui.queue;

public class CircleQueue {

    private int maxsize=16;
    private int last; //最后一个元素的下一个位置
    private int front;//当前第一个元素
    private int[] arr;

    public CircleQueue(int maxsize) {
        if(maxsize<=0){
            throw new RuntimeException("长度需要大于0");
        }
        this.maxsize = maxsize;
        arr=new int[maxsize];
        this.last=0;
        this.front=0;
    }
    private void push(int value){
        //先判断队列是否已满
        if(this.isFull()){
            throw new RuntimeException("队列已满");
        }
        int index=last % maxsize;
        arr[index]=value;
        last++;

    }
    private boolean isFull(){

        return this.last-this.front==maxsize;
    }

    private boolean isEmpty(){
        return front==last;
    }

    public int pop(){
        if(this.isEmpty()){
            throw new RuntimeException("队列没有数据");
        }
        int index=front % maxsize;
        int k=arr[index];
        front++;
        return k;
    }
    public int peek(){
        if(isEmpty()){
            throw new RuntimeException("队列没有数据");
        }
        int index=front % maxsize;
        int value=arr[index];
        return value;
    }
    public void println(){
        int start=front % maxsize;
        int end=(last-1) % maxsize;
        for(int i=start;i<=end;i++){
            System.out.println(arr[i]);
        }
    }
    public static void main(String[] args) {
        CircleQueue circleQueue = new CircleQueue(3);
        /*int i=0;
        while (true){
            circleQueue.push(1);
            System.out.println(circleQueue.pop());
            circleQueue.push(2);
            System.out.println(circleQueue.pop());
            circleQueue.push(3);
            System.out.println(circleQueue.pop());

            i++;
            if(i>100){
                break;
            }
        }*/
        circleQueue.push(1);
        circleQueue.push(2);
        circleQueue.push(3);
        circleQueue.println();


    }






}