Why does this work?

[Arthur Blair]

public static void main(String [] args) {

int[][] a = {{1,2},{0,1,2},{-1,0,2}}; // 1
Object[] obj = (Object[])a.clone(); // 2
for(int i = 0; i < obj.length; i++) { // 3
int[] ia = (int[])obj[i]; // 4
System.out.print(ia[i]); // 5
}

On line // 2 how is it possible to clone a two dimensional array and cast it into a 1 dimensional array? I really don't understand what is going on here. It would make sense conceptually if it said: Object[][] obj = (Object[][])a.clone(); but that isn't the case.

Could someone shed some light?
[ February 06, 2006: Message edited by: Arthur Blair ]

[marc weber]

Consider that in Java...

Multi-dimensional arrays are really just arrays of arrays.

Arrays are objects.

So if we have int[][] a, the array "a" is really just a single-dimension array of Objects. In particular, these Objects are int arrays.
[ February 06, 2006: Message edited by: marc weber ]

[Anju sethi]

it is still nt clear. could you please explain more with Eg.
Is there any good doc on cloning in 2-d array.

Please help

[Keith Lynn]

Consider the first line of code.

int[][] a = {{1,2},{0,1,2},{-1,0,2}}

Here what is being created is an array.

This array contains three elements, the first is an int array with 2 ints, the second is an int array with 3 ints, and the third is an int array with 3 ints.

As Mark said, there is no direct support for multidimensional arrays in Java. We build them as arrays of arrays.