import java.util.regex.Matcher;
import java.util.regex.Pattern;
public class MainClass {
public static void main(String args[]) {
Pattern p = Pattern.compile("(\\w+) (\\w+)");
StringBuffer sb = new StringBuffer();
String candidateString = "Jack Lee";
String replacement = "$2, $1";
Matcher matcher = p.matcher(candidateString);
matcher.matches();
matcher.appendReplacement(sb, replacement);
System.out.println(sb.toString());
}
}
//
Lee, Jack