loopqueue

import java.util.Arrays;

public class loopQueue <E>{

    public Object[] data=null;
    private int maxsize;
    private int rear;//队尾
    private int front;//
    private int size=0;

    public loopQueue(){

    }

    public loopQueue(int initsize){

        if(initsize>0){
            this.maxsize=initsize;
            data=new Object[initsize];
            rear=front=0;

        }

        else{

            throw new RuntimeException("初始化大小不能小于0");

        }

    }

    //
    public boolean isempty(){

        return size==0;
    }

    //insert
    public boolean add(E e){

        if(size==maxsize){

            throw new RuntimeException("the queue is full");
        }
        else{

            data[rear]=e;
            rear=(rear+1)%maxsize;
            size++;
            return true;
        }
    }

    //返回队首元素
    public E peek(){

        if(isempty()){
            throw new RuntimeException("this queue is empty");

        }
        else{

            return (E)data[front];
        }
    }

    //output
    public E poll(){

        if(isempty()){
            throw new RuntimeException("this queue is empty");

        }
        else{
            E e=(E)data[front];
            data[front]=null;
            front=(front+1)%maxsize;
            size--;
            return e;

        }

    }

    //
    public int getsize(){

        return size;
    }

    //
    public void clear(){
        Arrays.fill(data, null);
        size=0;
        front=0;
        rear=0;

    }

}