I would like to count occurrences of a character (for example the space: ' '
) in 2D Array, using stream. I was trying to find a solution. Here is my code, using a nested loops:
public int countFreeSpaces() {
int freeSpaces = 0;
for (int i = 0; i < height; i++) {
for (int j = 0; j < width; j++) {
if (board[j][i] == ' ') freeSpaces++;
}
}
return freeSpaces;
}
I believe this answer is slightly more expressive:
int freeSpaces = (int) Arrays.stream(board)
.map(CharBuffer::wrap)
.flatMapToInt(CharBuffer::chars)
.filter(i -> i == ' ')
.count();
Arrays.stream to stream over an existing array instead of the varargs method Stream.of. Also, String::new implies copying the char[] data, so I’d use .map(CharBuffer::wrap) .flatMapToInt(CharSequence::chars) instead. Contrary to what we might expect, in Java 8, CharBuffer.chars() is even implemented more efficient than String.chars().
char[] or a Character[], so I used IntStream instead. as you can see my answer publish time is before the OP says its type is a char[].
How about this?
// v--- create a Stream<char[]>
int spaces = (int) Stream.of(board)
.flatMapToInt(cells->IntStream.range(0, cells.length)
.filter(i -> cells[i] == ' '))
.count();
