? ArrayList<ArrayList><Double>> to double[][], and similarly for Integer

> Dear all, I tried a lot and didn't get an elegant

> solution to convert ArrayList<ArrayList><T>> to T[][],

> where T in my mind is Integer or Double. Any

> suggestions?

>

> I

which less elegant solution have you got so far?

r035198xa at 2007-7-14 22:36:49 >

I created a code that return a matrix with a Collection of Collections of a type.

public static <E> E[][] asMatrix(Collection<? extends Collection<E>> collection){

E[][] matrix=(E[][])new Object[collection.size()][];

int i=0;

for(Collection<E> subCollection:collection)

matrix[i++]=(E[])subCollection.toArray();

return matrix;

}

.

You can use this or create an method for each basic type, example:

public static int[][] asIntMatrix(Collection<? extends Collection<? extends Number>> collection){

int[][] matrix=new int[collection.size()][];

int i=0;

for(Collection<? extends Number> subCollection:collection) {

int [] column=new int[subCollection.size()];

int j=0;

for(Number number:subCollection)

matrix[i][j++]=number.intValue();

i++;

}

return matrix;

}

.

govisagod512a at 2007-7-14 22:36:49 >