Getting out integers and floats out of a String

Question

I'm trying to get out all numbers (integers and floats) out of a given String. For example:

"1.24 + 112 - 436 * 1.22 / 4 % 55"

I want to get 1.24 and the rest out of the string so I can do the math. Like this:

[1.24,+,112,-,436,1.22,/,4,%,55]

Ye you want reverse polish notation. Google for some parsers to do that. Also you got `Scanner` class that can help you in parsing as well as `Integer.parseInt()` and `Float.parseFloat()` — Antoniossss, May 13 '17 at 00:59

score 0 · Answer 1 · answered May 13 '17 at 01:17

Here you have regular expression for

public static void main(String[] args) {
        Pattern pat=Pattern.compile("\\d+\\.\\d++|\\d+|[-+=\\\\*/%]");
        String str="1.24+112-436*1.22/4%55";        
        Matcher matcher = pat.matcher(str);
        while(matcher.find()){
            System.out.println(matcher.group(0));
        }
    }

Output:

1.24
+
112
-
436
*
1.22
/
4
%
55

To handle negative numbers as well you will use Pattern.compile("-?\\d+\\.\\d++|-?\\d+|[-+=\\\\*/%]"); But there is a catch because there is no way to distict between x-y and x - y so you will have to assume that if there is no operator between 2 operands, there should be additon + resultion in x+(-y) and tha will be equal in both cases

But all in all, parsing math equasions can be complicated and tricky so you better use existing solution (google it out)

Getting out integers and floats out of a String

1 Answers1