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;
        
    }
    
}