Re: Array of something
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Lew <noone@lewscanon.com> writes:
Merciadri Luca wrote:
Here is a more complete description.
* I've got a Cell class which should allow me to define a state State for
every Cell instanciation. That is, I define
==
public class Cell
{
public enum State
{
DEAD, LIVING
}
public State state;
}
==
(these are either DEAD or LIVING `Cell' that will be instanciated).
* I want to compare the value of the state of a Cell with a State
`constant,' i.e. do something like
==
if (tableau.setOfCells[i][j].state == State.LIVING)
{
...
}
==
but compiler complains: `cannot find symbol State.'
That's because 'State' is a nested class - it has to be accessed
through its outer class. 'State' is a static member of 'Cell', not a
standalone class.
Thanks. This is part of the way I solved the problem.
Try 'Cell.State.LIVING', or else elevate 'State' to a top-level class:
------------------------------------
package tableaux;
public enum State
{
DEAD, LIVING
}
------------------------------------
------------------------------------
package tableaux;
public class Cell
{
public State state;
}
------------------------------------
Remember that public fields of a type are an antipattern in Java.
* In the last chunk of code, tableau is a Tableau element where I've
got a class `Tableau' defined like this:
==
public class Tableau
{
public Cell[][] setOfCells;
Bad name for something that is not a 'Set'.
public Tableau(int n, int s)
{
setOfCells = new Cell[n][n];
}
}
==
What does the constructor 's' argument contribute?
It contributed for another affectation in the constructor body. I
would have better put // ... so that you would have realized that the
's' argument was necessary.
and where tableau is created thanks to the call to the accessor:
==
Tableau tableau = new Tableau(n, s);
==
That is, my main goal is to create two instances of `Tableau': tableau
and tableau2, which should contain each one a `setOfCells' element,
which would be a n*n Cell array. This array would then be accessed
using habitual indices, and, an element of this Cell array being a
"habitual"?
Yes, say now tableau.setOfCells[x][y]. `habitual' -> generic way.
Cell, accessing a Cell would lead to the possibility of accessing its state.
OK
But what you show is an n x n array of 'null' references, so you have
nothing whose state you can access.
public class Tableau
{
/* p-p */ Cell[][] cells;
public Tableau(int n, int s)
{
cells = new Cell[n][n];
for ( int ix = 0; ix < n; ++ix )
for ( int jx = 0; jx < n; ++ix )
{
cells [ix] [jx] = getValue( ix, jx );
}
}
public void doSomething()
{
for ( int ix = 0; ix < cells.length; ++ix )
for ( int jx = 0; ix < cells [0].length; ++ix )
{
final Cell cell = cells [ix] [jx];
if ( cell != null )
{
process( cell.state );
}
}
}
}
If you don't handle error conditions, preferably via prevention, your
program will crash horribly and embarrass you beyond belief.
But why is that necessary? This might exactly be part of the solution
to my other thread, namely `Enum list.'
- --
Merciadri Luca
See http://www.student.montefiore.ulg.ac.be/~merciadri/
- --
Life is like a box of chocolate, you never know what you're gonna
get.
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