Question

I have a single string which looks like:

6
0 1 1 0 0
1 1 1 1 0
0 0 0 1 0
4
1 1 0 1 0
0 0 0 1 0
1 1 0 1 0
0 1 1 0 0

and would like to split into two different strings such as:

6
0 1 1 0 0
1 1 1 1 0
0 0 0 1 0

and the other string being:

4
1 1 0 1 0
0 0 0 1 0
1 1 0 1 0
0 1 1 0 0

Would I do this using regex? Or is there a better way?
note: apart from the 6 and 4 the others numbers will always be 1 or 0.

Answer 1

You want to split on newlines, but only when the following character(s) is only digit(s) then a newline.
Try this regex:

"\n(?=\\d+\\n)"

It uses a look ahead to assert the condition mentioned above.

Here’s some test code:

public static void main(String[] args) {
    String input = "6\n0 1 1 0 0\n1 1 1 1 0\n0 0 0 1 0\n4\n1 1 0 1 0\n0 0 0 1 0\n1 1 0 1 0\n0 1 1 0 0";
    String[] parts = input.split("\n(?=\\d+\\n)");
    System.out.println(Arrays.toString(parts));
}

Output:

[6
0 1 1 0 0
1 1 1 1 0
0 0 0 1 0, 4
1 1 0 1 0
0 0 0 1 0
1 1 0 1 0
0 1 1 0 0]