Array

[srinivas sridaragaddi]

  class B1{
public static void main(String args[]){
A[] a1=new A[1];
A[][] a2=new A[2][1];
A[][][] a3=new A[3][3][3];
System.out.println(a3[2][2][2]);
a1[0]=new A();
a2[0]=a2[1]=a1;
a3[0]=a3[1]=a3[2]=a2;
System.out.println(a3[2][2][2]);//1
}
}  

options:
prints null
prints nullnull
compile-time error
Run-time exception

answer:run-time exception

ArrayIndexOutOfBoundsException at line:1

Explain

[suresh mulagala]

Because a3 is being converted to a max of A[3][2][1] when you are doing

a3[0]=a3[1]=a3[2]=a2;

so the utmost you can do is a3[2][1][0]

[swati cha]

if i compile the above program i am gettein error like..

A cannot be resolved to a type
could you explain this.

[Srikanth Iyer]

in the above mentioned code your are tryiing to create and array of Type class A and thus you should declare a class named and thenn complie.

just add class a{} in your code and it will complie fine.

[Burkhard Hassel]

In the first part:
A[] a1=new A[1];
A[][] a2=new A[2][1];
A[][][] a3=new A[3][3][3];
System.out.println(a3[2][2][2]);

The arrays are created, and the default values (null) are put into their places.
Therefore the output is null.

Second part:

a1[0]=new A();
a2[0]=a2[1]=a1;
a3[0]=a3[1]=a3[2]=a2;
System.out.println(a3[2][2][2]);//1



a1 looks like this:
a1: { the new A() }

an array with only one element, length of the array is one.


When you say
a2[0]=a2[1]=a1;

a2 looks like:
a2: { a1, a1 }
Now, a2 no longer has the length of three because it has been reassigned.


and finally
a3[0]=a3[1]=a3[2]=a2;

a3 looks like:
a3: { a2, a2, a2 }



But when you want to have:
System.out.println(a3[2][2][2]);//1

Starting from left to right:
a3[2] points to a2 (all three elements of a3 are a2).

Therefore
a3[2] [2] is the same as
a2[2]
but a2 has only a2[0] and a2[1] (see bold line above), therefore the exception.


Perhaps draw the arrays on a sheet of paper.


Yours,
Bu.

[suresh mulagala]

Swathi try this...

 
class B1{
public static void main(String args[]){
A[] a1=new A[1];
A[][] a2=new A[2][1];
A[][][] a3=new A[3][3][3];
System.out.println(a3[2][2][2]);
a1[0]=new B1().new A();
a2[0]=a2[1]=a1;
a3[0]=a3[1]=a3[2]=a2;
System.out.println(a3[2][2][2]);//1}}  
}

class A {}
}
 

[dhwani mathur]

This was a superbb explanation

by Mr Burkhard Hassel !!

[srinivas sridaragaddi]

Thanks Burkhard for explaining so briefly....

Thank you for helping me understand many topics as you have replied to most of my posts...