How to Use Java Regex to Check If a String Contains Any Words from a Set

How can I use Java Regex to check if a string contains any specific words from a defined set?

In Java, you can use the built-in regular expressions (Regex) to efficiently determine if a string contains any words from a specified set. This can be particularly useful in scenarios like content moderation, input validation, or where certain triggers need to be identified.

import java.util.regex.*;

public class RegexExample {
    public static void main(String[] args) {
        String input = "This is a sample string containing some keywords.";
        String[] wordsToSearch = {"sample", "keywords", "test"};
        String regex = String.join("|", wordsToSearch);
        Pattern pattern = Pattern.compile(regex);
        Matcher matcher = pattern.matcher(input);
        boolean found = matcher.find();

        if (found) {
            System.out.println("The string contains at least one of the words from the set.");
        } else {
            System.out.println("No matches found.");
        }
    }
}

Causes

• The need to search for specific keywords within a larger body of text.
• Filtering content based on certain words for user-generated input.

Solutions

• Define a set of words that you want to search for.
• Use a regular expression pattern that matches any of these words.
• Utilize the `Pattern` and `Matcher` classes from the `java.util.regex` package to perform the search.

Mistake: Forgetting to escape special characters in regex words.

Solution: Use `Pattern.quote(word)` to escape any special characters.

Mistake: Using incorrect regex syntax which leads to unexpected results.

Solution: Double-check the regex pattern or test it using regex tester tools.