How to Reset the Pattern of a Regular Expression?

A regular expression pattern in Java is defined using the Pattern class, which is a component of the java.util.regex package. But sometimes, we may wish to reset the internal state of the Pattern object or use it again with a different input string. This helps to improve efficiency in instances where pattern matching occurs often by avoiding the need to recreate the Pattern object numerous times.

Resetting the Pattern of a Regular Expression in Java

We may reset the internal state of the Pattern object in Java using the reset() method of the Pattern class. When we want to match against several input strings using the same Pattern object again, this is helpful.

Let’s look at a simple example to understand how to reset a regular expression’s pattern in Java:

Java

// Java Program for Resetting the Pattern of a Regular Expression
import java.util.regex.*;

// Driver Class
public class PatternResetExample {
    // Main FUnction
      public static void main(String[] args)
    {
        // Create a Pattern object
        // It matches one or more than one digits
        Pattern pattern = Pattern.compile("\\d+");

        // Create a Matcher object
        Matcher matcher = pattern.matcher("8520");

        // Perform the match
        if (matcher.find()) {
            System.out.println("Match found: "+ matcher.group());
        }

        // Reset the Pattern for a different string
        matcher.reset("kkhgt5678");
        System.out.println("After resetting the Matcher ");

        // Perform the match again
        if (matcher.find()) {
            System.out.println("Match found: "+ matcher.group());
        }
    }
}

Output

Match found: 8520
After resetting the Matcher 
Match found: 5678

Explaination of the above Program:

1. Create a Pattern Object
2. Use the Matcher to Match against a String
3. Reset the Pattern for a Different String

This demonstrates the successful reset of the Pattern for a different input string.