Question

Here’s what I’ve done:

    while (sc.hasNext()) {
        String sLine = sc.nextLine();
        sLine.replaceAll("\\s", "");
        String[] scanned = sLine.split("");

My input is going to be something like this:

IF (2 -2 +) (3 2 *) (-1 4 +) (5 3 *)

What this means is irrelevant, but what the scanner does is store it in a string “as is”, first of all. Then I use the replaceAll function to remove all whitespace. I am then left with:

IF(2-2+)(32*)(-14+)(53*)

I then interpret this code using java and perform the calculation if no errors occur. My issue now is, that when I split the string into tokens, it’s going to make each “minus” sign its own token, but I want to somehow relate it with the integer following it so that token is still just an integer (now negative) and have no tokens with a minus sign in it. Is there an easy way to do such a thing?

Answer 1

You can use negative look-behind to split on empty string not preceded by a hyphen :-

str.split("(?<!-)");

This will not split on the empty string between - and 2, thus keeping them intact.

String str = "IF(2-2+)(32*)(-14+)(53*)";
String[] arr = str.split("(?<!-)");
System.out.println(Arrays.toString(arr));

Output: –

[, I, F, (, 2, -2, +, ), (, 3, 2, *, ), (, -1, 4, +, ), (, 5, 3, *, )]

Now you have -2 and -1 instead of having - as separate element.