public class RE

 RE r = new RE("a*b");

 boolean matched = r.match("aaaab");

 RE r = new RE("(a*)b");                  // Compile expression
 boolean matched = r.match("xaaaab");     // Match against "xaaaab"

 String wholeExpr = r.getParen(0);        // wholeExpr will be 'aaaab'
 String insideParens = r.getParen(1);     // insideParens will be 'aaaa'

 int startWholeExpr = r.getParenStart(0); // startWholeExpr will be index 1
 int endWholeExpr = r.getParenEnd(0);     // endWholeExpr will be index 6
 int lenWholeExpr = r.getParenLength(0);  // lenWholeExpr will be 5

 int startInside = r.getParenStart(1);    // startInside will be index 1
 int endInside = r.getParenEnd(1);        // endInside will be index 5
 int lenInside = r.getParenLength(1);     // lenInside will be 4

 String pattern = "([0-9]+)=\\1";

 **Characters**

   *unicodeChar*   Matches any identical unicode character
   \                    Used to quote a meta-character (like '*')
   \\                   Matches a single '\' character
   \0nnn                Matches a given octal character
   \xhh                 Matches a given 8-bit hexadecimal character
   \\uhhhh              Matches a given 16-bit hexadecimal character
   \t                   Matches an ASCII tab character
   \n                   Matches an ASCII newline character
   \r                   Matches an ASCII return character
   \f                   Matches an ASCII form feed character

 **Character Classes**

   [abc]                Simple character class
   [a-zA-Z]             Character class with ranges
   [^abc]               Negated character class

 **Standard POSIX Character Classes**

   [:alnum:]            Alphanumeric characters.
   [:alpha:]            Alphabetic characters.
   [:blank:]            Space and tab characters.
   [:cntrl:]            Control characters.
   [:digit:]            Numeric characters.
   [:graph:]            Characters that are printable and are also visible.
                        (A space is printable, but not visible, while an
                        `a' is both.)
   [:lower:]            Lower-case alphabetic characters.
   [:print:]            Printable characters (characters that are not
                        control characters.)
   [:punct:]            Punctuation characters (characters that are not letter,
                        digits, control characters, or space characters).
   [:space:]            Space characters (such as space, tab, and formfeed,
                        to name a few).
   [:upper:]            Upper-case alphabetic characters.
   [:xdigit:]           Characters that are hexadecimal digits.

 **Non-standard POSIX-style Character Classes**

   [:javastart:]        Start of a Java identifier
   [:javapart:]         Part of a Java identifier

 **Predefined Classes**

   .         Matches any character other than newline
   \w        Matches a "word" character (alphanumeric plus "_")
   \W        Matches a non-word character
   \s        Matches a whitespace character
   \S        Matches a non-whitespace character
   \d        Matches a digit character
   \D        Matches a non-digit character

 **Boundary Matchers**

   ^         Matches only at the beginning of a line
   $         Matches only at the end of a line
   \b        Matches only at a word boundary
   \B        Matches only at a non-word boundary

 **Greedy Closures**

   A*        Matches A 0 or more times (greedy)
   A+        Matches A 1 or more times (greedy)
   A?        Matches A 1 or 0 times (greedy)
   A{n}      Matches A exactly n times (greedy)
   A{n,}     Matches A at least n times (greedy)
   A{n,m}    Matches A at least n but not more than m times (greedy)

 **Reluctant Closures**

   A*?       Matches A 0 or more times (reluctant)
   A+?       Matches A 1 or more times (reluctant)
   A??       Matches A 0 or 1 times (reluctant)

 **Logical Operators**

   AB        Matches A followed by B
   A|B       Matches either A or B
   (A)       Used for subexpression grouping
  (?:A)      Used for subexpression clustering (just like grouping but
             no backrefs)

 **Backreferences**

   \1    Backreference to 1st parenthesized subexpression
   \2    Backreference to 2nd parenthesized subexpression
   \3    Backreference to 3rd parenthesized subexpression
   \4    Backreference to 4th parenthesized subexpression
   \5    Backreference to 5th parenthesized subexpression
   \6    Backreference to 6th parenthesized subexpression
   \7    Backreference to 7th parenthesized subexpression
   \8    Backreference to 8th parenthesized subexpression
   \9    Backreference to 9th parenthesized subexpression