Regular expressions in Java

Regex

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

/**
 *
 */
public class REGEX {
    
    public static void main(String[] args) {
        
        
        // Get the text of the first match from a regex.
        
        String testString = "There are 14 penguins sitting on 3 chairs";
        
        String regex = "\\d+";  //1 or more digits. Escape the special char \
        
        Pattern pattern = Pattern.compile(regex);
    
        Matcher m = pattern.matcher(testString);
        
       
        System.out.println(m.find());    // true
    
        System.out.println(m.group());   // The text matched. Call .find() first
    
        System.out.println(m.start()); // Start index of the previous match. Char 10
        System.out.println(m.end()); // End index of the previous match. Char 12
    
        System.out.println(m.find(15));    // Start looking at char 15. true
    
        System.out.println(m.start()); // Start index of the previous match - now 32
        System.out.println(m.end()); // End index of the previous match - now 34
        
        System.out.println(m.matches());   // true if there's one+ matches
        
        
        Matcher m2 = pattern.matcher("There are 12 penguins, 15 cats, 34 dogs, and 1 ferret.");
        
        while ( m2.find()) {
            System.out.println(m2.group());    // 12,  15,  24,  1
        }
    }
}