character sequencePattern A matcher is created from a pattern by invoking the pattern's Pattern.matcher(java.lang.CharSequence)
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(java.lang.StringBuffer)replaceAll(java.lang.String)
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 java.lang.IllegalStateException
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()reset(java.lang.CharSequence)
Instances of this class are not safe for use by multiple concurrent threads.
MatchResultMatchResult with the state of this matcherThis method causes this matcher to lose information about the groups of the last match that occurred. The matcher's position in the input is maintained and its last append position is unaffected.
newPattern
The new pattern used by this matcherjava.lang.IllegalArgumentException
If newPattern is nullResetting a matcher discards all of its explicit state information and sets its append position to zero. The matcher's region is set to the default region, which is its entire character sequence. The anchoring and transparency of this matcher's region boundaries are unaffected.
Resetting a matcher discards all of its explicit state information and sets its append position to zero. The matcher's region is set to the default region, which is its entire character sequence. The anchoring and transparency of this matcher's region boundaries are unaffected.
input
The new input character sequencejava.lang.IllegalStateException
If no match has yet been attempted,
or if the previous match operation failedCapturing groups are indexed from left to right, starting at one. Group zero denotes the entire pattern, so the expression m.start(0) is equivalent to m.start().
group
The index of a capturing group in this matcher's patternjava.lang.IllegalStateException
If no match has yet been attempted,
or if the previous match operation failedjava.lang.IndexOutOfBoundsException
If there is no capturing group in the pattern
with the given indexjava.lang.IllegalStateException
If no match has yet been attempted,
or if the previous match operation failedCapturing groups are indexed from left to right, starting at one. Group zero denotes the entire pattern, so the expression m.end(0) is equivalent to m.end().
group
The index of a capturing group in this matcher's patternjava.lang.IllegalStateException
If no match has yet been attempted,
or if the previous match operation failedjava.lang.IndexOutOfBoundsException
If there is no capturing group in the pattern
with the given indexFor a matcher m with input sequence s, the expressions m.group() and s.substring(m.start(), m.end()) are equivalent.
Note that some patterns, for example a*, match the empty string. This method will return the empty string when the pattern successfully matches the empty string in the input.
java.lang.IllegalStateException
If no match has yet been attempted,
or if the previous match operation failedFor a matcher m, input sequence s, and group index g, the expressions m.group(g) and s.substring(m.start(g), m.end(g)) are equivalent.
Capturing groups are indexed from left to right, starting at one. Group zero denotes the entire pattern, so the expression m.group(0) is equivalent to m.group().
If the match was successful but the group specified failed to match any part of the input sequence, then null is returned. Note that some groups, for example (a*), match the empty string. This method will return the empty string when such a group successfully matches the empty string in the input.
group
The index of a capturing group in this matcher's patternjava.lang.IllegalStateException
If no match has yet been attempted,
or if the previous match operation failedjava.lang.IndexOutOfBoundsException
If there is no capturing group in the pattern
with the given indexGroup zero denotes the entire pattern by convention. It is not included in this count.
Any non-negative integer smaller than or equal to the value returned by this method is guaranteed to be a valid group index for this matcher.
This method starts at the beginning of this matcher's region, or, if a previous invocation of the method was successful and the matcher has not since been reset, at the first character not matched by the previous match.
If the match succeeds then more information can be obtained via the start, end, and group methods.
If the match succeeds then more information can be obtained via the
start, end, and group methods, and subsequent
invocations of the find()
java.lang.IndexOutOfBoundsException
If start is less than zero or if start is greater than the
length of the input sequence. Like the matches method, this method always starts
at the beginning of the region; unlike that method, it does not
require that the entire region be matched.
If the match succeeds then more information can be obtained via the start, end, and group methods.
String for the specified
String.
This method produces a String that will work
as a literal replacement s in the
appendReplacement method of the MatcherString produced will match the sequence of characters
in s treated as a literal sequence. Slashes ('\') and
dollar signs ('$') will be given no special meaning.
s The string to be literalizedThis method performs the following actions:
It reads characters from the input sequence, starting at the
append position, and appends them to the given string buffer. It
stops after reading the last character preceding the previous match,
that is, the character at index start()
It appends the given replacement string to the string buffer.
It sets the append position of this matcher to the index of
the last character matched, plus one, that is, to end()
The replacement string may contain references to subsequences
captured during the previous match: Each occurrence of
$g will be replaced by the result of
evaluating group(g).
The first number after the $ is always treated as part of
the group reference. Subsequent numbers are incorporated into g if
they would form a legal group reference. Only the numerals '0'
through '9' are considered as potential components of the group
reference. If the second group matched the string "foo", for
example, then passing the replacement string "$2bar" would
cause "foobar" to be appended to the string buffer. A dollar
sign ($) may be included as a literal in the replacement
string by preceding it with a backslash (\$).
Note that backslashes (\) and dollar signs ($) in the replacement string may cause the results to be different than if it were being treated as a literal replacement string. Dollar signs may be treated as references to captured subsequences as described above, and backslashes are used to escape literal characters in the replacement string.
This method is intended to be used in a loop together with the
appendTail and find methods. The
following code, for example, writes one dog two dogs in the
yard to the standard-output stream:
Pattern p = Pattern.compile("cat");
Matcher m = p.matcher("one cat two cats in the yard");
StringBuffer sb = new StringBuffer();
while (m.find()) {
m.appendReplacement(sb, "dog");
}
m.appendTail(sb);
System.out.println(sb.toString());sb
The target string bufferreplacement
The replacement stringjava.lang.IllegalStateException
If no match has yet been attempted,
or if the previous match operation failedjava.lang.IndexOutOfBoundsException
If the replacement string refers to a capturing group
that does not exist in the pattern This method reads characters from the input sequence, starting at
the append position, and appends them to the given string buffer. It is
intended to be invoked after one or more invocations of the appendReplacement(java.lang.StringBuffer,java.lang.String)
sb
The target string buffer This method first resets this matcher. It then scans the input
sequence looking for matches of the pattern. Characters that are not
part of any match are appended directly to the result string; each match
is replaced in the result by the replacement string. The replacement
string may contain references to captured subsequences as in the appendReplacement(java.lang.StringBuffer,java.lang.String)
Note that backslashes (\) and dollar signs ($) in the replacement string may cause the results to be different than if it were being treated as a literal replacement string. Dollar signs may be treated as references to captured subsequences as described above, and backslashes are used to escape literal characters in the replacement string.
Given the regular expression a*b, the input "aabfooaabfooabfoob", and the replacement string "-", an invocation of this method on a matcher for that expression would yield the string "-foo-foo-foo-".
Invoking this method changes this matcher's state. If the matcher is to be used in further matching operations then it should first be reset.
replacement
The replacement string This method first resets this matcher. It then scans the input
sequence looking for a match of the pattern. Characters that are not
part of the match are appended directly to the result string; the match
is replaced in the result by the replacement string. The replacement
string may contain references to captured subsequences as in the appendReplacement(java.lang.StringBuffer,java.lang.String)
Note that backslashes (\) and dollar signs ($) in the replacement string may cause the results to be different than if it were being treated as a literal replacement string. Dollar signs may be treated as references to captured subsequences as described above, and backslashes are used to escape literal characters in the replacement string.
Given the regular expression dog, the input "zzzdogzzzdogzzz", and the replacement string "cat", an invocation of this method on a matcher for that expression would yield the string "zzzcatzzzdogzzz".
Invoking this method changes this matcher's state. If the matcher is to be used in further matching operations then it should first be reset.
replacement
The replacement stringstart parameter and end at the
index specified by the end parameter.
Depending on the transparency and anchoring being used (see
useTransparentBounds and
useAnchoringBounds), certain constructs such
as anchors may behave differently at or around the boundaries of the
region.
start
The index to start searching at (inclusive)end
The index to end searching at (exclusive)java.lang.IndexOutOfBoundsException
If start or end is less than zero, if
start is greater than the length of the input sequence, if
end is greater than the length of the input sequence, or if
start is greater than end.This method returns true if this matcher uses transparent bounds, false if it uses opaque bounds.
See useTransparentBounds for a
description of transparent and opaque bounds.
By default, a matcher uses opaque region boundaries.
useTransparentBounds(boolean)Invoking this method with an argument of true will set this matcher to use transparent bounds. If the boolean argument is false, then opaque bounds will be used.
Using transparent bounds, the boundaries of this matcher's region are transparent to lookahead, lookbehind, and boundary matching constructs. Those constructs can see beyond the boundaries of the region to see if a match is appropriate.
Using opaque bounds, the boundaries of this matcher's region are opaque to lookahead, lookbehind, and boundary matching constructs that may try to see beyond them. Those constructs cannot look past the boundaries so they will fail to match anything outside of the region.
By default, a matcher uses opaque bounds.
b a boolean indicating whether to use opaque or transparent
regionshasTransparentBounds()This method returns true if this matcher uses anchoring bounds, false otherwise.
See useAnchoringBounds for a
description of anchoring bounds.
By default, a matcher uses anchoring region boundaries.
useAnchoringBounds(boolean)Invoking this method with an argument of true will set this matcher to use anchoring bounds. If the boolean argument is false, then non-anchoring bounds will be used.
Using anchoring bounds, the boundaries of this matcher's region match anchors such as ^ and $.
Without anchoring bounds, the boundaries of this matcher's region will not match anchors such as ^ and $.
By default, a matcher uses anchoring region boundaries.
b a boolean indicating whether or not to use anchoring bounds.hasAnchoringBounds()Returns true if the end of input was hit by the search engine in the last match operation performed by this matcher.
When this method returns true, then it is possible that more input would have changed the result of the last search.
Returns true if more input could change a positive match into a negative one.
If this method returns true, and a match was found, then more input could cause the match to be lost. If this method returns false and a match was found, then more input might change the match but the match won't be lost. If a match was not found, then requireEnd has no meaning.