How to count the number of matches for a regex in java?

How to count the number of matches for a regex in java?

To count the number of matches for a regular expression in Java, you can use the java.util.regex package, specifically the Pattern and Matcher classes. Here's a step-by-step guide on how to do this:

  • Import the required classes:
import java.util.regex.Matcher; import java.util.regex.Pattern;
  • Compile the regular expression pattern using Pattern.compile(). Make sure to provide the desired regex pattern as a string.
String regex = "your_regex_here"; Pattern pattern = Pattern.compile(regex);

Replace "your_regex_here" with the actual regular expression pattern you want to use.

  • Create a Matcher object by calling the matcher() method on the Pattern object and passing the input text you want to search for matches in.
String inputText = "your_input_text_here"; Matcher matcher = pattern.matcher(inputText);

Replace "your_input_text_here" with the text you want to search for matches in.

  • Iterate through the matches using a while loop and the find() method of the Matcher object. Inside the loop, increment a counter for each match found.
int matchCount = 0; while (matcher.find()) { matchCount++; }
  • The matchCount variable now contains the total number of matches for your regular expression in the input text.

Here's a complete example:

import java.util.regex.Matcher; import java.util.regex.Pattern; public class RegexMatchCount { public static void main(String[] args) { String regex = "\\b\\w+\\b"; // Example regex for matching words String inputText = "This is a sample sentence with some words."; Pattern pattern = Pattern.compile(regex); Matcher matcher = pattern.matcher(inputText); int matchCount = 0; while (matcher.find()) { matchCount++; } System.out.println("Number of matches: " + matchCount); } }

In this example, the regular expression "\\b\\w+\\b" matches words in the input text. The program counts and prints the number of matches, which is 8 in this case. You can replace the regex and input text with your specific requirements.

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