【基础算法】用数组结构实现大小固定的循环队列

【思想简述】 定义存储数组和队头、队尾指针和已经入队中元素个数，做好队满和队空判断条件。这里queueSize可以使用rear和front关系进行替换。

队列基础类：

public class queueByArray {
    //初识储存空间和队头、堆尾指针
    Integer[] arr;
    Integer front;
    Integer rear;
    Integer queueSize;
 
    public  queueByArray(Integer initSize){
        if(initSize < 0){
            throw new IllegalArgumentException("初始化大小小于零");
        }
        arr = new Integer[initSize];
        front = rear = queueSize = 0;
    }
 
    //判断队是否为空
    public boolean isEmpty(){
        return queueSize==0 ? true : false;
    }
    //判断队是否满
    public boolean isFull(){
        return (queueSize == arr.length-1) ? true : false;
    }
    //进队
    public void inQueue(Integer num){
        //队满
        if(this.isFull()) {
            throw new IllegalArgumentException("队列已满！");
        }
 
        arr[rear] = num;
        rear = rear == arr.length-1 ? 0 : rear +1; //当队列不满，rear后移越界时，返回起点
        queueSize++;
 
    }
    //出队
    public Integer outQueue(){
        //队空
        if(this.isEmpty()){
            throw new IllegalArgumentException("队列为空！");
        }
        Integer tem = arr[front];
        front = front == arr.length-1 ? 0 : front+1;
        queueSize--;
        return tem;
    }
}

测试类：

public class queueByArrayTest {
    public static void  main(String[] args){
        queueByArray queue = new queueByArray(6);
        System.out.println(queue.isEmpty());    //true
 
        queue.inQueue(3);
        queue.inQueue(4);
        queue.inQueue(6);
        queue.inQueue(9);
        queue.inQueue(7);
 
        System.out.println(queue.isEmpty());     //false
        queue.inQueue(13);
        try {
            queue.inQueue(14);                  //队满
        }catch (Exception e){
            System.out.println(e);
        }
 
        while(!queue.isEmpty()){
            System.out.println(queue.outQueue());          //3,4,6,9,7
        }
 
        try {
            System.out.println(queue.outQueue());        //"队列为空"
 
        }catch (Exception e){
            System.out.println(e);
        }
 
        queue.inQueue(15);
        queue.inQueue(16);
        queue.inQueue(17);
 
        System.out.println(queue.front);     //该处属性应该封装,当前为测试
        System.out.println(queue.rear);     //该处属性应该封装
 
 
    }
 
}