Java Regular Expressions parameters example

Java Regular Expressions parameters example

characters

.
Any character (may or may not match line terminators)

\d
A digit: [0-9]

\D
A non-digit: [^0-9]

\s
A whitespace character: [ \t\n\x0B\f\r]

\S
A non-whitespace character: [^\s]

\w
A word character: [a-zA-Z_0-9]

\W
A non-word character: [^\w]

Match:

\d matches all digits
\s matches spaces
\w matches word characters

Alternatively, a capital letter means the opposite:

\D matches non-digits
\S matches non-spaces
\W matches non-word characters

Boundary Construct Description

^ The beginning of a line
$ The end of a line
\b A word boundary
\B A non-word boundary
\A The beginning of the input
\G The end of the previous match
\Z The end of the input but for the final terminator, if any
\z The end of the input

Example:

private final String REGEX = "\\d"; // a single digit

Pattern p = Pattern.compile(REGEX);
       //  get a matcher object
       Matcher m = p.matcher(INPUT);
       int count = 0;
       while(m.find()) {
           count++;
           System.out.println("Match number "
                              + count);
           System.out.println("start(): "
                              + m.start());
           System.out.println("end(): "
                              + m.end());
      }