Matcher.appendReplacement method : Matcher « Regular Expressions « Java Tutorial

1. Java Tutorial
2. Regular Expressions
3. Matcher

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