Matcher (Java Platform SE 7 )

An engine that performs match operations on a character sequence by interpreting a Pattern

A matcher is created from a pattern by invoking the pattern’s matcher method. Once created, a matcher can be used to
perform three different kinds of match operations:

  • The matches method attempts to match the entire
    input sequence against the pattern.

  • The lookingAt method attempts to match the
    input sequence, starting at the beginning, against the pattern.

  • The find method scans the input sequence looking for
    the next subsequence that matches the pattern.

Each of these methods returns a boolean indicating success or failure.
More information about a successful match can be obtained by querying the
state of the matcher.

A matcher finds matches in a subset of its input called the
region. By default, the region contains all of the matcher’s input.
The region can be modified via theregion method and queried
via the regionStart and regionEnd
methods. The way that the region boundaries interact with some pattern
constructs can be changed. See useAnchoringBounds and useTransparentBounds
for more details.

This class also defines methods for replacing matched subsequences with
new strings whose contents can, if desired, be computed from the match
result. The appendReplacement and appendTail methods can be used in tandem in order to collect
the result into an existing string buffer, or the more convenient replaceAll method can be used to create a string in which every
matching subsequence in the input sequence is replaced.

The explicit state of a matcher includes the start and end indices of
the most recent successful match. It also includes the start and end
indices of the input subsequence captured by each capturing group in the pattern as well as a total
count of such subsequences. As a convenience, methods are also provided for
returning these captured subsequences in string form.

The explicit state of a matcher is initially undefined; attempting to
query any part of it before a successful match will cause an IllegalStateException to be thrown. The explicit state of a matcher is
recomputed by every match operation.

The implicit state of a matcher includes the input character sequence as
well as the append position, which is initially zero and is updated
by the appendReplacement method.

A matcher may be reset explicitly by invoking its reset()
method or, if a new input sequence is desired, its reset(CharSequence) method. Resetting a
matcher discards its explicit state information and sets the append position
to zero.

Instances of this class are not safe for use by multiple concurrent