Constructor not being called

I was asked to explain why the line

Code:

---

System.out.println("" + x[2].getN());

---

wont work. I figure the constructor is not being triggered but the why, beats me. Anyone care to explain?

Code:

---

class Num{
    private int n;
    public int getN(){ return n;}
    public Num( ){ n = 4; }
}
public class Main {
  public static void main( String[] args){
    Num [] x = new Num[7];
    System.out.println("" + x.length); 
    System.out.println("" + x[2].getN());             
  }
}

---

If I'm not mistaken you're probably getting a NullPointerException?

You've shown that Num holds an array of Num objects but you haven't assigned a Num object to the array
Try

Code:

---

Num [] x = new Num[7] ;
int i = 0 ;
    while(i < 7)
    {
        x[i] = new Num() ;
        i++ ;
    }

---

this should call the empty constructor of the object Num to the array and create the object of it.
The "=" the assigns the object to your array. Use a loop then for the rest of the elements. The line should work then!

Sorry if this confuses you it's the first time I've provided advice and it's the best I can explain it to you :-)

I think you made a perfect explanation.

Expression

Code:

---

Num [] x = new Num[7]

---

only tells de JVM to allocate a block of contiguous memory. Num constructor is NOT called.

Albert.