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 threads.
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