nulllpointer exception in 2 dimensional string array

Hi
I have a simple code which goes like

String[][] attr=new String[20][];
attr[0][0]="hi";
System.out.println("attr00"+attr[0][0]);

I am getting a nullpointer exception in the third line at runtime. Can you please explain.
Even if i remove the second line I still get the same thing.
Shouldnt hav the array elements be initilized with default values?

Thanks
Utsav.

Remember that a 2 dimensional array is just an array of arrays and that the default value of an object is null.

You're not getting the exception at the third line, but at the second line. Add this line just after creating the array and before the assignment and you'll see why: System.out.println(java.util.Arrays.deepToString(attr));

Hi
Thanks for youe quick responses
So If I want assign the string "hi" at 0,0 location ,how do I do that?

utsav gupta wrote:
So If I want assign the string "hi" at 0,0 location ,how do I do that?

In order to assign an element to a certain location, that array location has to exist. Remember an two-dimensional array, is an array of arrays in java -- you never instantiated any of the arrays for the array of arrays.

Henry