How to match the text file against multiple regex patterns and count the number of occurences of these patterns?

Question

I want to find and count all the occurrences of the words unit, device, method, module in every line of the text file separately. That's what I've done, but I don't know how to use multiple patterns and how to count the occurrence of every word in the line separately? Now it counts only occurrences of all words together for every line. Thank you in advance!

private void countPaterns() throws IOException {

    Pattern nom = Pattern.compile("unit|device|method|module|material|process|system");

    String str = null;      

    BufferedReader r = new BufferedReader(new FileReader("D:/test/test1.txt")); 

    while ((str = r.readLine()) != null) {
        Matcher matcher = nom.matcher(str);

        int countnomen = 0;
        while (matcher.find()) {
            countnomen++;
        }

        //intList.add(countnomen);
        System.out.println(countnomen + " davon ist das Wort System");
    }
    r.close();
    //return intList;
}

Please add useful tags, such as what language you're using. "count", "matcher", and "find-occurences" are not useful for this question. — miken32
– miken32, Commented Oct 29, 2015 at 20:32

anubhava · Accepted Answer · 2015-10-29 20:49:10Z

3

Better to use a word boundary and use a map to keep counts of each matched keyword.

Pattern nom = Pattern.compile("\\b(unit|device|method|module|material|process|system)\\b");

String str = null;
BufferedReader r = new BufferedReader(new FileReader("D:/test/test1.txt"));
Map<String, Integer> counts = new HashMap<>();

while ((str = r.readLine()) != null) {
    Matcher matcher = nom.matcher(str);

    while (matcher.find()) {
        String key = matcher.group(1);
        int c = 0;
        if (counts.containsKey(key))
            c = counts.get(key);
        counts.put(key, c+1)
    }
}
r.close();

System.out.println(counts);

answered Oct 29, 2015 at 20:49

anubhava

790k67 gold badges603 silver badges671 bronze badges

Sign up to request clarification or add additional context in comments.

2 Comments

Oleg_08 Over a year ago

Thanks! it works this way very good, but the only problem that I get the number of occurrences for the whole txt file. But I need to get this number for every new line of the text separately. Before your change it has worked for every line

anubhava Over a year ago

If you want count per line then add counts.clear() after Matcher matcher = nom.matcher(str); line and make sure to print it inside the outer while loop.

hfontanez · Accepted Answer · 2022-02-17 17:20:31Z

0

Here's a Java 9 (and above) solution:

public static void main(String[] args) {
    List<String> expressions = List.of("(good)", "(bad)");
    String phrase = " good  bad     bad good   good bad bad bad";

    for (String regex : expressions) {
        Pattern gPattern = Pattern.compile(regex);
        Matcher matcher = gPattern.matcher(phrase);
        long count = matcher.results().count();
        System.out.println("Pattern \"" + regex + "\" appears " + count + (count == 1 ? " time" : " times"));
    }
}

Outputs

Pattern "(good)" appears 3 times
Pattern "(bad)" appears 5 times

answered Feb 17, 2022 at 17:20

hfontanez

6,2082 gold badges29 silver badges43 bronze badges

Collectives™ on Stack Overflow

How to match the text file against multiple regex patterns and count the number of occurences of these patterns?

2 Answers 2

2 Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

2 Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related