A negative look ahead : Introduction « Regular Expressions « Java Tutorial

1. Java Tutorial
2. Regular Expressions
3. Introduction

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

public class MainClass {
  public static void main(String args[]) throws Exception {
    // define the pattern
    String regex = "First (?!Second)[A-Z]\\w+";

    // compile the pattern
    Pattern pattern = Pattern.compile(regex);

    String candidate = "First Second asdf ";
    candidate += "John third, John second asdf, ";
    candidate += "John Fourth.";

    Matcher matcher = pattern.matcher(candidate);

    String tmp = null;

    while (matcher.find()) {
      tmp = matcher.group();
      System.out.println("MATCH:" + tmp);
    }
  }
}