3-D Arrays

[Radith]

The NetBeans compiler will not let me initialize a 3D array in the following
way:

int[][][] a2 = {
{ 1, 2, 3, },
{ 4, 5, 6, },
{ 7, 8, 9, },
};

WHAT IS THE CORRECT METHOD TO DO THIS?

Cheers.

 

[Stefan Schulz]

The NetBeans compiler will not let me initialize a 3D array in the
following way:

int[][][] a2 = {
{ 1, 2, 3, },
{ 4, 5, 6, },
{ 7, 8, 9, },
};

WHAT IS THE CORRECT METHOD TO DO THIS?

Turn of the ALL-CAPS and use a three dimensional initializer, what you
have until now is two-dimensional. (Do you intend to use a two-dimensional
array with each dimension having size 3?)

For further assistance, see replies in comp.lang.java.help, the
appropriate newsgroup for this kind of problem.

X-Post & F'up2 comp.lang.java.help

 

[Ishmael Rufus]

Do you notice that your array is 2 demensional? I'm assuming it is a
cube with 3 lengths on each side.

 

[Eric Sosman]

The NetBeans compiler will not let me initialize a 3D array in the following
way:

int[][][] a2 = {
{ 1, 2, 3, },
{ 4, 5, 6, },
{ 7, 8, 9, },
};

The initializer is only 2D.

WHAT IS THE CORRECT METHOD TO DO THIS?

WHAT DO YOU MEAN BY "THIS?" (Oh, sorry; I shouldn't
shout at people.)

You could write

int[][][] a2 = { {
{ 1, 2, 3, },
{ 4, 5, 6, },
{ 7, 8, 9, },
}, };

.... but that would be rather pointless: You'd have a 3D
array, but the first dimension would have only one index.
(Roughly speaking, you'd have a "[1][3][3]" array.)

Here's a suggestion: Each pair of [brackets] in the
array dimensions matches up with one level of {braces} in
the initializer, so give each brace level its own level
of indentation:

int[][][] a2 =
{
{
{ 1, 2, 3, },
{ 4, 5, 6, },
{ 7, 8, 9, },
},
{
{ 3, 1, 4, },
{ 1, 5, 9, },
},
{
{ 2, 7, 1, 8, },
{ 2, 8, 1, },
{ 8, 2, 4, 5, 9, 0, 5, },
},
};

You may eventually decide to adopt a more compressed
style, but a scheme like this may help you keep your wits
about you while your confidence grows.

Note that the sample above creates a "ragged" array.
The ability to have such things is a consequence of the
fact that Java really doesn't have multi-dimensional arrays
at all. It does, however, have singly-dimensioned arrays
whose elements can themselves be singly-dimensioned arrays,
and the elements of *those* can be singly-dimensioned arrays,
and so on:

a2 is an array with three elements, all arrays
a2[0] is an array with three elements, all arrays
a2[0][0] is an array with three `int' elements
... as are a2[0][1] and a2[0][2]
a2[1] is an array with two elements, both arrays
a2[1][0] is an array with three `int' elements
... as is a2[1][1]
a2[2] is an array with three elements, all arrays
a2[2][0] is an array with four `int' elements
a2[2][1] is an array with three `int' elements
a2[2][2] is an array with seven `int' elements

If you ponder this for a while, you'll see why the
"complete brace style" is a necessity in Java: there is
no way Java can infer where the level transitions occur
by counting elements or any such.

 

[Wendy S]

int[][][] a2 = {
{ 1, 2, 3, },
{ 4, 5, 6, },
{ 7, 8, 9, },
};

That's not 3D, it only has rows and columns, no 'depth'. (It's merely an
array of arrays at this point.) Try it as int[][] and it should compile.

If you really want an array of arrays of arrays... then each of the integers
above needs to be an array.