An engine that performs match operations on a
by interpreting a
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:
matchesmethod attempts to match the entire input sequence against the pattern.
lookingAtmethod attempts to match the input sequence, starting at the beginning, against the pattern.
findmethod 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 the
region method and queried
methods. The way that the region boundaries interact with some pattern
constructs can be changed. See
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
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
A matcher may be reset explicitly by invoking its
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
Instances of this class are not safe for use by multiple concurrent threads.