Complex data types in java -

i have designed data type called bingocard create random bingo card. i'm trying make bingocard array keep getting error on line: system.out.println(currentcard[i].tostring());

i'm wondering if i've created array correctly or doing wrong? in advance.

public class bingogame { private int[] counter; private boolean done = false; private int numofcards; private int fastestcard;  public bingogame(int num){ numofcards = num; counter = new int[numofcards]; }   public int play(){ for(int a=0;a<numofcards;a++){     counter[a] = 0; }  bingocard[] currentcard = new bingocard[numofcards]; while(!done){     for(int i=0;i<numofcards;i++){         system.out.println("this current card:");         system.out.println(currentcard[i].tostring());          int currentnum = (int)(math.random() * 75) + 1;         counter[i]++;         currentcard[i].currentnumber(currentnum);         currentcard[i].bingo();         if(currentcard[i].bingo()){             done = true;         }         fastestcard = i;     }  } return counter[fastestcard]; }  } 

elements in object array null default. need instantiate elements before attempting invoke methods

for (int = 0; < numofcards; i++) {     currentcard[i] = new bingocard();     ... }