Can I convert integers found in a string to integers, each with their own variable? (Java)

Question

Let's say you have a string with the phrase ("He has 2 cats")

Is there a way for the program to take out the integers in the string and assign each integer to a variable?

It shows how to make it into an array but I want to make each integer into a variable. However, it looks almost like what I want. — Sharon, Nov 05 '20 at 16:44
The thought of putting things into different variables usually is a beginner's mistake. Unless the structure of the text is always the same and therefore determinable, an array is the better way to achieve this. And the examples can easily be adjusted for variables btw. — maio290, Nov 05 '20 at 16:48
@Sharon: what if there are 12 numbers in the string? Will you have 12 variables? — Joachim Sauer, Nov 05 '20 at 16:49
It's not possible to declare/assign an arbitrary number of variables based on a runtime input. However, you can add each found integer to an array or a Collection, which will allow you to access each one individually. — user1717259, Nov 05 '20 at 16:50
@Sharon: so what happens once you've written your code and someone calls the method with a string that contains 13 methods? What is supposed to happen in that case? — Joachim Sauer, Nov 05 '20 at 19:31

Frederik Pietzko · Answer 1 · 2020-11-05T17:11:06.957

3

Something like this should work.

import java.util.regex.Matcher;
import java.util.regex.Pattern;
import java.util.List;
import java.util.ArrayList;

public class RegexExamples {
    public static void main(String[]args) {
        Pattern p = Pattern.compile("\\d+");
        Matcher m = p.matcher("He has 2 cats");
        List<Integer> numbers = new ArrayList<Integer>();
        while(m.find()) {
            numbers.add(Integer.parseInt(m.group()));
        }
    }
}

edited Nov 05 '20 at 17:11

answered Nov 05 '20 at 16:47

Frederik Pietzko

113
6

1

OP asked to store each in a separate variable, not a List – Aharon K Nov 05 '20 at 16:51
@AharonK Although OP did, this is the only acceptable solution for this problem. Each time you would want to have iterated variable names (e.g. number_0, number_1, ...), an array would be the better solution by any means. – maio290 Nov 05 '20 at 16:58
A `List` does not exist. It should be a `List`. – MC Emperor Nov 05 '20 at 16:58
@MCEmperor mb. Changed the answer accordingly. – Frederik Pietzko Nov 05 '20 at 17:12

score 1 · Answer 2 · answered Nov 05 '20 at 17:44

I think the most variable-like way to handle this would be to parse out the Integers and put them into a Map.

Something like this, note that it might break on certain unexpected inputs. If you have any question on a certain part of this code feel free to ask:

import java.util.LinkedHashMap;
import java.util.Map;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
public class Main {

    public static void main(String[] args) {
        String input = "He has 2 dogs, 5 cats, wait.. make that 6 cats, and 1000 mice!";
        Map<String, Integer> map = parseNounCounts(input);
        for (Map.Entry<String, Integer> entry : map.entrySet()) {
            System.out.println(entry.getKey() + " : " + entry.getValue());
        }
    }

    private static final Pattern NOUN_COUNT_PATTERN = Pattern.compile("(?:^|\\s)(\\d+)\\s+([a-zA-Z]*)");

    /**
     * Parses integers, and the words they precede, from the given input string and returns the map of
     * words to their preceding integer count in order of discovery.
     */
    public static LinkedHashMap<String, Integer> parseNounCounts(String input) {
        Matcher matcher = NOUN_COUNT_PATTERN.matcher(input);
        LinkedHashMap<String, Integer> map = new LinkedHashMap<>();
        while (matcher.find()) {
            String key = matcher.group(2);
            int value = Integer.parseInt(matcher.group(1));
            if (map.containsKey(key)) {
                String newKey;
                for (int i = 2; map.containsKey(newKey = key + '#' + String.valueOf(i)); i++)
                    ;
                key = newKey;
            }
            map.put(key, value);
        }
        return map;
    }
}

Running main prints the following:

dogs : 2
cats : 5
cats#2 : 6
mice : 1000

Can I convert integers found in a string to integers, each with their own variable? (Java)

2 Answers2