public static final  void main(String[] args) 
{
    int matches = 0;
    String numberExpression = "\\d+";
    String exactMatch = "2010";
    String containsMatches =
   "  2001 was the movie before 2010, which takes place before 2069 the book ";
    Pattern pattern   = null;
    PatternMatcherInput input;
    PatternCompiler compiler;
    PatternMatcher matcher;
    MatchResult result;
    // Create AwkCompiler and AwkMatcher instances.
    compiler = new AwkCompiler();
    matcher  = new AwkMatcher();
    // Attempt to compile the pattern.  If the pattern is not valid,
    // report the error and exit.
    try {
      pattern = compiler.compile(numberExpression);
    } catch(MalformedPatternException e) {
      System.err.println("Bad pattern.");
      System.err.println(e.getMessage());
      System.exit(1);
    }
    // Here we show the difference between the matches() and contains()
    // methods().  Compile the program and study the output to reinforce
    // in your mind what the methods do.
    System.out.println("Input: " + exactMatch);
    // The following should return true because exactMatch exactly matches
    // numberExprssion.
    if(matcher.matches(exactMatch, pattern))
      System.out.println("matches() Result: TRUE, EXACT MATCH");
    else
      System.out.println("matches() Result: FALSE, NOT EXACT MATCH");
    System.out.println("\nInput: " + containsMatches);
    // The following should return false because containsMatches does not
    // exactly match numberExpression even though its subparts do.
    if(matcher.matches(containsMatches, pattern))
      System.out.println("matches() Result: TRUE, EXACT MATCH");
    else
      System.out.println("matches() Result: FALSE, NOT EXACT MATCH");
    // Now we call the contains() method.  contains() should return true
    // for both strings.
    System.out.println("\nInput: " + exactMatch);
    if(matcher.contains(exactMatch, pattern)) {
      System.out.println("contains() Result: TRUE");
      // Fetch match and print.
      result = matcher.getMatch();
      System.out.println("Match: " + result);
    } else
      System.out.println("contains() Result: FALSE");
    System.out.println("\nInput: " + containsMatches);
    if(matcher.contains(containsMatches, pattern)) {
      System.out.println("contains() Result: TRUE");
      // Fetch match and print.
      result = matcher.getMatch();
      System.out.println("Match: " + result);
    } else
      System.out.println("contains() Result: FALSE");
    // In the previous example, notice how contains() will fetch only first 
    // match in a string.  If you want to search a string for all of the
    // matches it contains, you must create a PatternMatcherInput object
    // to keep track of the position of the last match, so you can pick
    // up a search where the last one left off.
    input   = new PatternMatcherInput(containsMatches);
    System.out.println("\nPatternMatcherInput: " + input);
    // Loop until there are no more matches left.
    while(matcher.contains(input, pattern)) {
      // Since we're still in the loop, fetch match that was found.
      result = matcher.getMatch();  
      ++matches;
      System.out.println("Match " + matches + ": " + result);
    }
}

A common mistake is to confuse the behavior of the matches() and contains() methods. matches() tests to see if a string exactly matches a pattern whereas contains() searches for the first pattern match contained somewhere within the string. When used with a PatternMatcherInput instance, the contains() method allows you to search for every pattern match within a string by using a while loop.