如何使用对象类型的空引用在Java中填充数组

Question

我想要一个类型为Reservation的对象数组（我的项目中的一个类）。要做到这一点，我需要初始化数组，首先将其所有位置初始化为null）然后当某些条件满足时使用此数组充当Room对象的成员变量，但是当我尝试时我不断得到NullPointerException访问该表，让我说明一下：

public class Room  {

static int rCode=100;

private int roomID;
         //kodikos domatiou paragetai me basi tin roomid
 Reservation[] diathes;//here is the table of Reservation objects that i want containing null at first

private int maxAtoma;//final? static?

boolean k;

private double priceatom;//timi domatiou ana atomo

Reservation res;//reference to a reservation object

 public Domatio(int maxPeople,double pricePAtom)
  {
     this.roomID=rCode++; //this.roomid=roomid

     this.maxAtoma=maxPeople;

     this.priceatom=pricePAtom;

     Reservation[] diathes=new Reservation[30]; 
    for(int i=0; i<diathes.length; i++)
    {

    diathes[i]=null;//i fill the array with null references to Reservation objects
   }
}  



 boolean addreserve(Reservation res )
{

    boolean kAdd=false;
    int countExit=0;
    for(int i=0; i<30; i++)
    {
        if(this.diathes[i]!=null || res.getAtomaOReserv()>this.maxAtoma){//here is the problem at this line where i access the diathes[] table null PointerException but is required of me to have it initialized with null,throwing the exception wont solve the problem

        kAdd=false;
      }
         else{

            for( int z = res.getAfixi();z<res.getAfixi()+res.getMeresDiam(); z++){//if these conditions meet i give a reference to a Reservation object to the analogous table element

              this.diathes[z]=res;

              countExit++;
            }
             kAdd=true;


            res.antistixisidToDom(this);//antistoixi tou deikti tis reservation ,dom sto current room pou egine i kratisi
        }     



            if(countExit!=0){
                break;//exodos apo broxo an egine i kratisi
        }

    }

   return kAdd;

}