How can I convert an Array [1, 2, 3, 4, 5, 6, 7 ,8, 9, 10, 11, 12] to a 2D-Array looking like this?
[[1, 2, 3],
[4, 5, 6],
[7, 8, 9],
[10, 11, 12]]
Always 3 Numbers in a row.
What I have tried returns the first line correct, but the other lines are the same as the first.
for (int i = 0; i < array.length; ++i) {
for (int k = 0; k < 3; ++k) {
result[k][i] = args[i];
}
This shall work for you:
for (int i = 0; i < array.length/3; ++i) {
for (int k = 0; k < 3; ++k) {
result[i][k] = args[i*3+k];
}
}
Here we are computing the source index array based on i*3+k to keep on getting the next index value.
An one-line and debatably readable solution would be:
int[] foo = {1, 2, 3, 4, 5, 6, 7 ,8, 9, 10, 11, 12};
System.out.println(
Arrays.deepToString(
new int[][]
{
Arrays.copyOfRange(foo, 0, 3),
Arrays.copyOfRange(foo, 3, 6),
Arrays.copyOfRange(foo, 6, 9),
Arrays.copyOfRange(foo, 9, 12)
}
)
);
Output
[[1, 2, 3], [4, 5, 6], [7, 8, 9], [10, 11, 12]]
Note
Method Arrays.copyOfRange is only available from Java 6.
Otherwise you have to use System.arrayCopy which returns void (not applicable to example as is).
arr1 - array with input numbers
arr2 - array with output numbers
for(int i=0;i<arr1.length;i++)
for(int j=0;j<3;j++)
arr2[i][j]=arr1[i*3+j];
