How to find the last index using regex of a particular word in a String?

Last Updated : 25 Jan, 2024

To find the last index of a particular word in a string using regular expressions in Java, you can use the Matcher class along with a regular expression that captures the desired word.

Java Program to last index Using the Regex of a Particular Word in a String

Below is the implementation of the last index Using the Regex of a Particular Word in a String:

Java 
// Java Program to Find last index 
// Using the Regex of a Particular Word in a String
import java.util.regex.Matcher;
import java.util.regex.Pattern;

// Driver Class
public class LastIndexOfWordUsingRegex {
    // Main Function
    public static void main(String[] args) {
        String inputString = "This is a sample sentence with a particular word. Another occurrence of the word.";

        // Specify the word you want to find
        String wordToFind = "word";

        // Create a pattern with the word and the end-of-input anchor
        String regex = "\\b" + Pattern.quote(wordToFind) + "\\b";
        Pattern pattern = Pattern.compile(regex);

        // Create a matcher for the input string
        Matcher matcher = pattern.matcher(inputString);

        // Find the last occurrence of the word
        int lastIndex = -1;
        while (matcher.find()) {
            lastIndex = matcher.start();
        }

        // Print the last index or indicate if the word is not found
        if (lastIndex != -1) {
            System.out.println("Last index of '" + wordToFind + "': " + lastIndex);
        } else {
            System.out.println("'" + wordToFind + "' not found in the string.");
        }
    }
}

Output:

Last index of 'word': 76

Explanation of the above Program:

  • The regular expression \\b is used to denote a word boundary.
  • Pattern.quote(wordToFind) is used to escape any special characters in the word.
  • The end-of-input anchor $ is used to ensure that the match occurs at the end of the input.
  • The Matcher iterates through the input string using find(), updating the lastIndex each time a match is found.

Note: This approach assumes that you want to match whole words. If you want to find occurrences within other words, you may need to adjust the regular expression accordingly.

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