Arrays

[Mubeen Shaik]

Hi All,

Please explain this code. How it works?


==========================================================

  
class A11 {
 
public String toString() {
 
return "A11";
 
}}
 

class A12 {
  public static void main(String[] arg) {
 
    A11[]     a1 = new A11[1];         // 1
 
    A11[][]   a2 = new A11[2][];       // 2
 
    A11[][][] a3 = new A11[3][][];     // 3
 
    a1[0] = new A11();                 // 4
 

    a2[0] = a2[1] = a1;                // 5
 
    a3[0] = a3[1] = a3[2] = a2;        // 6
 

    System.out.print(a3[2][1][0]);     // 7
}}
 

========================================================

Thanks in advance,
Mubeen Shaik.

[Soumy Kumar]

Hi..
I also don't have any idea of how its working..
Help with answers please.

[Mike Gershman]

a1 refers to a 1 dimensional array, type A11[], of one component containing a reference of type A11 to the one and only instance of a class A11 object.

a2 is a 2 dimensional array, type A11[][], with two rows. Each row is that same one dimensional array referred to by a1.

a3 is a 3 dimensional array, type A11[][][], with 3 slices. Each slice is that same 2 dimensional array referred to by a2.

so a3's maximum subscripts are a3[2][1][0]


a2 actually refers to a 1 dimensional array of 2 references of type A11[].
Both references are set to the same value by copying the value of a1.

a3 actually refers to a 1 dimensional array of 3 references of type A11[][]. All 3 references are set to the same value by copying the value of a2.

The output is "A11".

[ December 15, 2004: Message edited by: Mike Gershman ]
[ December 15, 2004: Message edited by: Mike Gershman ]

[Mubeen Shaik]

Mike,

Thanks for the detailed explanation. But how the output is "A11".

Thanks in advance,
Mubeen Shaik

[Barry Gaunt]

Mubeen, what's the type of the object that a3[2][1][0] refers to?

[Mubeen Shaik]

Barry,

It refers to the type "class". Please correct me if i am wrong.

Thanks,
Mubeen Shaik

[Barry Gaunt]

I was expecting you to answer "a3[2][1][0] refers to an object of type (or class) A11". So when you try to print such an object the class' toString() method would be called. And what does the toString() method do for class A11? It returns the string "A11".

[Jugal Hans]

so when you try to print such an object the class' toString() method would be called.

why would the method be implicitly called ?

[Mike Gershman]

When you use an object reference "r" where a String is needed, "r" is treated like "r.toString()", which returns a String.