Question

I need help with Regex to extract numbers from a string that is missing decimals.

Input
2 4.0 6.0 7 8 4.60

Output
2 7 8

Edit: Another follow up question to this regarding Regex and Java. Lets say that I want to add stuff to what I found (what I really want is taking 2 4.0 7.5 and turn it into 2.0 4.0 7.5, meaning adding missing .0 to the ones without a decimal), how would I do that and still keep the same untouched things of my String?

Answer 1

For 2nd question: –

Here’s the solution for your 2nd requirement: –

String str = "2 4.0 6.0 7.5 8 4.60";
str = str.replaceAll("(?<=^|[ ])(\\d+)(?=$|[ ])", "$1.0");

System.out.println(str);  // Prints 2.0 4.0 6.0 7.5 8.0 4.60

---

For 1st question : –

You can use this Regex: –

(?<=^|[ ])(\\d+)(?=$|[ ])

This will match any sequence of digits followed and preceded by a space. Also, it matches digits at the end of the strings with the use of ^ and $.

Here’s the implementation : –

    String str = "2 4.0 6.0 7 8 4.60";
    Pattern pattern = Pattern.compile("(?<=^|[ ])(\\d+)(?=[$ ])");

    Matcher matcher = pattern.matcher(str);

    while (matcher.find()) {
        System.out.print(matcher.group(1) + " ");
    }

Output : –

2 7 8