This question is related to How do I copy a 2 Dimensional array in Java?
But how would you copy an array using streams in Java 8 / 9?
This is what I came up with:
static int[][] cloneArray(int[][] array) {
return IntStream.range(0, array.length).collect(
() -> new int[array.length][],
(ints, i) -> ints[i] = array[i].clone(),
(ints, i) -> {});
}
Is there a more elegant or performant way to copy a 2D array using streams?
return Arrays.stream(x).map(r->Arrays.copyOf(r, r.length)).toArray(int[][]::new);
I think this is an improvement because you're not allocating a nxm array then replacing all of the m length ones with a copy.
.clone call with System.arraycopy or at the very least, ditch the array[0].length and leave that part empty..clone slower than System.arraycopy? Thank you for the suggestion to leave the array[0].length empty.System.arraycopy will be the fastest because it allocates everything upfront.You can do it straight-forwardly using
static int[][] cloneArray(int[][] x) {
return Arrays.stream(x).map(int[]::clone).toArray(int[][]::new);
}
Note that this works for any ElementType with a public method ElementType clone(), like
static ElementType[] cloneArray(ElementType[] x) {
return Arrays.stream(x).map(ElementType::clone).toArray(ElementType[]::new);
}
and in your case, ElementType happens to be int[].
