MultiDimensional Arrays

[Ann Sebastian]

class A13 {}
class A14 {
public static void main(String[] arg) {
A13[] a1 = new A13[1]; // 1
A13[][] a2 = new A13[2][1]; // 2
A13[][][] a3 = new A13[3][3][3]; // 3
System.out.print(a3[2][2][2]); // 4
a1[0] = new A13(); // 5
a2[0] = a2[1] = a1; // 6
a3[0] = a3[1] = a3[2] = a2; // 7
System.out.print(a3[2][2][2]); // 8
}}

Line 3 outputs null which is fine,because arrays declared within the method are initialised to null..

Could any body tell me why line number 8 throws up null pointer exception?

[raghava yelamkonda]

Hi all
a3[0] = a3[1] = a3[2] = a2;
now a3[2] is not a 2*2 array ( 2 rows and 2 columns)
it just 1*2 array
u r trying to retrive a3[2][2][2]
a3[2][x][y] is nothing but a2[x][y]
a3[2][2][y] is nothing but a2[2][y]

but a2 dose not have 2 nd row since it is having 0th row and 1th row (array index starts at 0)
correct me if iam wrong
thank you