使用正则表达式在java中提取子字符串

import java.util.regex.Matcher;
import java.util.regex.Pattern;

public class SubstringExtractor {
    public static void main(String[] args) {
        String input = "This is a sample input string.";
        String regex = "is ([a-zA-Z])";
        
        Pattern pattern = Pattern.compile(regex);
        Matcher matcher = pattern.matcher(input);
        
        if (matcher.find()) {
            System.out.println("Matched: " + matcher.group(1));
        } else {
            System.out.println("No match found.");
        }
    }
}