java.lang.Objectjava.util.regex.Matcher
All Implemented Interfaces:
MatchResult
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 the region 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.
Mike
- McCloskeyMark
- ReinholdJSR-51
- Expert Group1.4
- JSR-51
- Field Summary | ||
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Pattern | parentPattern | The Pattern object that created this Matcher. |
int[] | groups | The storage used by groups. They may contain invalid values if a group was skipped during the matching. |
int | from | The range within the sequence that is to be matched. Anchors will match at these "hard" boundaries. Changing the region changes these values. |
int | to | |
int | lookbehindTo | Lookbehind uses this value to ensure that the subexpression match ends at the point where the lookbehind was encountered. |
CharSequence | text | The original string being matched. |
static final int | ENDANCHOR | Matcher state used by the last node. NOANCHOR is used when a match does not have to consume all of the input. ENDANCHOR is the mode used for matching all the input. |
static final int | NOANCHOR | |
int | acceptMode | |
int | first | The range of string that last matched the pattern. If the last match failed then first is -1; last initially holds 0 then it holds the index of the end of the last match (which is where the next search starts). |
int | last | |
int | oldLast | The end index of what matched in the last match operation. |
int | lastAppendPosition | The index of the last position appended in a substitution. |
int[] | locals | Storage used by nodes to tell what repetition they are on in a pattern, and where groups begin. The nodes themselves are stateless, so they rely on this field to hold state during a match. |
boolean | hitEnd | Boolean indicating whether or not more input could change the results of the last match. If hitEnd is true, and a match was found, then more input might cause a different match to be found. If hitEnd is true and a match was not found, then more input could cause a match to be found. If hitEnd is false and a match was found, then more input will not change the match. If hitEnd is false and a match was not found, then more input will not cause a match to be found. |
boolean | requireEnd | Boolean indicating whether or not more input could change a positive match into a negative one. If requireEnd is true, and a match was found, then more input could cause the match to be lost. If requireEnd is 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. |
boolean | transparentBounds | If transparentBounds is true then the boundaries of this matcher's region are transparent to lookahead, lookbehind, and boundary matching constructs that try to see beyond them. |
boolean | anchoringBounds | If anchoringBounds is true then the boundaries of this matcher's region match anchors such as ^ and $. |
Constructor: |
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Method from java.util.regex.Matcher Summary: |
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appendReplacement, appendTail, charAt, end, end, find, find, getSubSequence, getTextLength, group, group, group, groupCount, hasAnchoringBounds, hasTransparentBounds, hitEnd, lookingAt, match, matches, pattern, quoteReplacement, region, regionEnd, regionStart, replaceAll, replaceFirst, requireEnd, reset, reset, search, start, start, toMatchResult, toString, useAnchoringBounds, usePattern, useTransparentBounds |
Methods from java.lang.Object: |
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clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait |
Method from java.util.regex.Matcher Detail: |
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This method performs the following actions: The replacement string may contain references to subsequences captured during the previous match: Each occurrence of ${name} or $g will be replaced by the result of evaluating the corresponding group(name) or group(g) respectively. For $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()); |
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 method in order to copy the remainder of the input sequence. |
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Capturing 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(). |
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() method will start at the first character not matched by this match. |
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For 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. |
For 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. |
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 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 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. |
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. |
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. |
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. |
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If the match succeeds then more information can be obtained via the start, end, and group methods. |
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String for the specified
String .
This method produces a String that will work
as a literal replacement s in the
appendReplacement method of the Matcher class.
The String produced will match the sequence of characters
in s treated as a literal sequence. Slashes ('\') and
dollar signs ('$') will be given no special meaning. |
start 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. |
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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 method. 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. |
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 method. 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. |
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. |
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. |
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. |
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Capturing 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(). |
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Returns the string representation of this matcher. The
string representation of a |
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. |
This 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. |
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. |