如何使用正则表达式查找非标准订单中出现的模式？

Question

I have a need to be able to read a string and extract numerical values of different types and group them. However, these numbers may appear in any order. For example, I have two types of liquids (toxic and non-toxic). the string will have between zero and n occurrences of either type, and in no guaranteed order. but I want to be able to sum up each type. Example String input is:

10ml toxic abcdeljsdg 15 ml toxic alkewag 25 ml non-toxic lkjasdg 30ml toxic 40 ml non-toxic

should return groupings of:

10ml toxic, 15 ml toxic, 30ml toxic, 25 ml non-toxic, 40 ml non-toxic

because i want to be able to add them up to get a total of 55ml toxic and 65ml non-toxic.

How do I write a regular expression pattern to be able to group these out?

I have messed around with using ? to be non-greedy, but that doesn't seem to work with numerical values.

Answer 1

By using regex you can group them like this:

String data = "10ml toxic abcdeljsdg 15 ml toxic alkewag 25 ml non-toxic lkjasdg 30ml toxic 40 ml non-toxic";
Pattern pattern= Pattern.compile("\\d+[\\s]?ml toxic");
Matcher matcher= pattern.matcher(data);
while(matcher.find()) {
    System.out.println(matcher.group());
}

The result will be:

 10ml toxic
 15 ml toxic
 30ml toxic

You can do the same with non-toxic. Then you can keep continue with calculate the sum of each group.

Answer 2

The RegEx you should use is

(\\d+(?=\\s*ml\\s*toxic))|(\\d+(?=\\s*ml\\s*non-toxic))

\\\\d+ will match any number of digits greater than 1

(?=) includes the following phrase in the match but not in the results

\\\\s*ml\\\\s*toxic matches any number of spaces, ml , any number of spaces again, toxic .

| represents the or operator in regex, so

|(\\\\d+(?=\\\\s*ml\\\\s*non-toxic)) can be added to find the non-toxic volume.

Matcher.group(1) is going to include values that matched the left half of the expression, and Matcher.group(2) for the right half.

String pattern = "(\\d+(?=\\s*ml\\s*toxic))|(\\d+(?=\\s*ml\\s*non-toxic))";
String str = "10ml toxic abcdeljsdg 15 ml toxic alkewag 25 ml non-toxic lkjasdg 30ml toxic 40 ml non-toxic";

Pattern p = Pattern.compile(pattern);
Matcher m = p.matcher(str);

int sum1 = 0;
int sum2 = 0;
while(m.find()){
    if (m.group(1)!=null)
        sum1 += Integer.parseInt(m.group(1));
    if (m.group(2)!=null)
        sum2 += Integer.parseInt(m.group(2));
}
System.out.println("Toxic = " + sum1);
System.out.println("Non-Toxic = " + sum2);

This will output

Toxic = 55
Non-Toxic = 65

And don't forget to import

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

Answer 3

Another possibility:

String data = "10ml toxic abcdeljsdg 15 ml toxic alkewag 25 ml non-toxic lkjasdg 30ml toxic 40 ml non-toxic";
Pattern pattern= Pattern.compile("(\\d+)[\\s]*(ml)\\s+((?:non-)?toxic)");
Matcher matcher= pattern.matcher(data);
while(matcher.find()) {
    System.out.println(matcher.group(1) + matcher.group(2) + " " + matcher.group(3));
}

This will output:

10ml toxic
15ml toxic
25ml non-toxic
30ml toxic
40ml non-toxic

You still need to group the results by matcher.group(3) :

Map<String,List<String>> map = new HashMap<>();
Matcher matcher= pattern.matcher(data);
while(matcher.find()) {
    String value = matcher.group(1);
    String unit = matcher.group(2);
    String key = matcher.group(3);
    List<String> list = map.get(key);
    if (list == null) {
        list = new ArrayList<>();
        map.put(key, list);
    }
    list.add(value + unit);
}
System.out.println(map);

Output:

{toxic=[10ml, 15ml, 30ml], non-toxic=[25ml, 40ml]}