java.util.regex: public final class: Matcher

java.util.regex
public final class: Matcher [javadoc | source]

java.lang.Object
   java.util.regex.Matcher

All Implemented Interfaces:
MatchResult

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 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. 
author: Mike -  McCloskey
author: Mark -  Reinhold
author: JSR-51 -  Expert Group
since: 1.4 - 
spec: JSR-51 - 









    







    
Field Summary
  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:
 Matcher() {

}
No default constructor.
 Matcher(Pattern parent,
    CharSequence text) {
        this.parentPattern = parent;
        this.text = text;
        // Allocate state storage
        int parentGroupCount = Math.max(parent.capturingGroupCount, 10);
        groups = new int[parentGroupCount * 2];
        locals = new int[parent.localCount];
        // Put fields into initial states
        reset();
}
All matchers have the state used by Pattern during a match.









    Method from java.util.regex.Matcher Summary:

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:

clone,   equals,   finalize,   getClass,   hashCode,   notify,   notifyAll,   toString,   wait,   wait,   wait
Method from java.util.regex.Matcher Detail:
 public Matcher appendReplacement(StringBuffer sb,
    String replacement) {
        // If no match, return error
        if (first <  0)
            throw new IllegalStateException("No match available");
        // Process substitution string to replace group references with groups
        int cursor = 0;
        StringBuilder result = new StringBuilder();
        while (cursor <  replacement.length()) {
            char nextChar = replacement.charAt(cursor);
            if (nextChar == '\\') {
                cursor++;
                nextChar = replacement.charAt(cursor);
                result.append(nextChar);
                cursor++;
            } else if (nextChar == '$') {
                // Skip past $
                cursor++;
                // A StringIndexOutOfBoundsException is thrown if
                // this "$" is the last character in replacement
                // string in current implementation, a IAE might be
                // more appropriate.
                nextChar = replacement.charAt(cursor);
                int refNum = -1;
                if (nextChar == '{') {
                    cursor++;
                    StringBuilder gsb = new StringBuilder();
                    while (cursor <  replacement.length()) {
                        nextChar = replacement.charAt(cursor);
                        if (ASCII.isLower(nextChar) ||
                            ASCII.isUpper(nextChar) ||
                            ASCII.isDigit(nextChar)) {
                            gsb.append(nextChar);
                            cursor++;
                        } else {
                            break;
                        }
                    }
                    if (gsb.length() == 0)
                        throw new IllegalArgumentException(
                            "named capturing group has 0 length name");
                    if (nextChar != '}')
                        throw new IllegalArgumentException(
                            "named capturing group is missing trailing '}'");
                    String gname = gsb.toString();
                    if (ASCII.isDigit(gname.charAt(0)))
                        throw new IllegalArgumentException(
                            "capturing group name {" + gname +
                            "} starts with digit character");
                    if (!parentPattern.namedGroups().containsKey(gname))
                        throw new IllegalArgumentException(
                            "No group with name {" + gname + "}");
                    refNum = parentPattern.namedGroups().get(gname);
                    cursor++;
                } else {
                    // The first number is always a group
                    refNum = (int)nextChar - '0';
                    if ((refNum <  0)||(refNum  > 9))
                        throw new IllegalArgumentException(
                            "Illegal group reference");
                    cursor++;
                    // Capture the largest legal group string
                    boolean done = false;
                    while (!done) {
                        if (cursor  >= replacement.length()) {
                            break;
                        }
                        int nextDigit = replacement.charAt(cursor) - '0';
                        if ((nextDigit <  0)||(nextDigit  > 9)) { // not a number
                            break;
                        }
                        int newRefNum = (refNum * 10) + nextDigit;
                        if (groupCount() <  newRefNum) {
                            done = true;
                        } else {
                            refNum = newRefNum;
                            cursor++;
                        }
                    }
                }
                // Append group
                if (start(refNum) != -1 && end(refNum) != -1)
                    result.append(text, start(refNum), end(refNum));
            } else {
                result.append(nextChar);
                cursor++;
            }
        }
        // Append the intervening text
        sb.append(text, lastAppendPosition, first);
        // Append the match substitution
        sb.append(result);
        lastAppendPosition = last;
        return this;
}
Implements a non-terminal append-and-replace step.

 This 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()  - 1.  

   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
${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());
 public StringBuffer appendTail(StringBuffer sb) {
        sb.append(text, lastAppendPosition, getTextLength());
        return sb;
}
Implements a terminal append-and-replace step.

 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.  
 char charAt(int i) {
        return text.charAt(i);
}
Returns this Matcher's input character at index i.
 public int end() {
        if (first <  0)
            throw new IllegalStateException("No match available");
        return last;
}
Returns the offset after the last character matched.  
 public int end(int group) {
        if (first <  0)
            throw new IllegalStateException("No match available");
        if (group  > groupCount())
            throw new IndexOutOfBoundsException("No group " + group);
        return groups[group * 2 + 1];
}
Returns the offset after the last character of the subsequence
captured by the given group during the previous match operation.

 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().  
 public boolean find() {
        int nextSearchIndex = last;
        if (nextSearchIndex == first)
            nextSearchIndex++;
        // If next search starts before region, start it at region
        if (nextSearchIndex <  from)
            nextSearchIndex = from;
        // If next search starts beyond region then it fails
        if (nextSearchIndex  > to) {
            for (int i = 0; i <  groups.length; i++)
                groups[i] = -1;
            return false;
        }
        return search(nextSearchIndex);
}
Attempts to find the next subsequence of the input sequence that matches
the pattern.

 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.  
 public boolean find(int start) {
        int limit = getTextLength();
        if ((start <  0) || (start  > limit))
            throw new IndexOutOfBoundsException("Illegal start index");
        reset();
        return search(start);
}
Resets this matcher and then attempts to find the next subsequence of
the input sequence that matches the pattern, starting at the specified
index.

 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.  
 CharSequence getSubSequence(int beginIndex,
    int endIndex) {
        return text.subSequence(beginIndex, endIndex);
}
Generates a String from this Matcher's input in the specified range.
 int getTextLength() {
        return text.length();
}
Returns the end index of the text.
 public String group() {
        return group(0);
}
Returns the input subsequence matched by the previous match.

 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.  
 public String group(int group) {
        if (first <  0)
            throw new IllegalStateException("No match found");
        if (group <  0 || group  > groupCount())
            throw new IndexOutOfBoundsException("No group " + group);
        if ((groups[group*2] == -1) || (groups[group*2+1] == -1))
            return null;
        return getSubSequence(groups[group * 2], groups[group * 2 + 1]).toString();
}
Returns the input subsequence captured by the given group during the
previous match operation.

 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.  
 public String group(String name) {
        if (name == null)
            throw new NullPointerException("Null group name");
        if (first <  0)
            throw new IllegalStateException("No match found");
        if (!parentPattern.namedGroups().containsKey(name))
            throw new IllegalArgumentException("No group with name < " + name + " >");
        int group = parentPattern.namedGroups().get(name);
        if ((groups[group*2] == -1) || (groups[group*2+1] == -1))
            return null;
        return getSubSequence(groups[group * 2], groups[group * 2 + 1]).toString();
}
Returns the input subsequence captured by the given
named-capturing group during the previous
match operation.

 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.  
 public int groupCount() {
        return parentPattern.capturingGroupCount - 1;
}
Returns the number of capturing groups in this matcher's pattern.

 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.  
 public boolean hasAnchoringBounds() {
        return anchoringBounds;
}
Queries the anchoring of region bounds 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.
 public boolean hasTransparentBounds() {
        return transparentBounds;
}
Queries the transparency of region bounds for this matcher.

 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.
 public boolean hitEnd() {
        return hitEnd;
}
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.
 public boolean lookingAt() {
        return match(from, NOANCHOR);
}
Attempts to match the input sequence, starting at the beginning of the
region, against the pattern.

 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.  
 boolean match(int from,
    int anchor) {
        this.hitEnd = false;
        this.requireEnd = false;
        from        = from <  0 ? 0 : from;
        this.first  = from;
        this.oldLast = oldLast <  0 ? from : oldLast;
        for (int i = 0; i <  groups.length; i++)
            groups[i] = -1;
        acceptMode = anchor;
        boolean result = parentPattern.matchRoot.match(this, from, text);
        if (!result)
            this.first = -1;
        this.oldLast = this.last;
        return result;
}
Initiates a search for an anchored match to a Pattern within the given
bounds. The groups are filled with default values and the match of the
root of the state machine is called. The state machine will hold the
state of the match as it proceeds in this matcher.
 public boolean matches() {
        return match(from, ENDANCHOR);
}
Attempts to match the entire region against the pattern.

 If the match succeeds then more information can be obtained via the
start, end, and group methods.  
 public Pattern pattern() {
        return parentPattern;
}
Returns the pattern that is interpreted by this matcher.
 public static String quoteReplacement(String s) {
        if ((s.indexOf('\\') == -1) && (s.indexOf('$') == -1))
            return s;
        StringBuilder sb = new StringBuilder();
        for (int i=0; i< s.length(); i++) {
            char c = s.charAt(i);
            if (c == '\\' || c == '$') {
                sb.append('\\');
            }
            sb.append(c);
        }
        return sb.toString();
}
Returns a literal replacement 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.
 public Matcher region(int start,
    int end) {
        if ((start <  0) || (start  > getTextLength()))
            throw new IndexOutOfBoundsException("start");
        if ((end <  0) || (end  > getTextLength()))
            throw new IndexOutOfBoundsException("end");
        if (start  > end)
            throw new IndexOutOfBoundsException("start  > end");
        reset();
        from = start;
        to = end;
        return this;
}
Sets the limits of this matcher's region. The region is the part of the
input sequence that will be searched to find a match. Invoking this
method resets the matcher, and then sets the region to start at the
index specified by the 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.
 public int regionEnd() {
        return to;
}
Reports the end index (exclusive) of this matcher's region.
The searches this matcher conducts are limited to finding matches
within  regionStart  (inclusive) and
 regionEnd  (exclusive).
 public int regionStart() {
        return from;
}
Reports the start index of this matcher's region. The
searches this matcher conducts are limited to finding matches
within  regionStart  (inclusive) and
 regionEnd  (exclusive).
 public String replaceAll(String replacement) {
        reset();
        boolean result = find();
        if (result) {
            StringBuffer sb = new StringBuffer();
            do {
                appendReplacement(sb, replacement);
                result = find();
            } while (result);
            appendTail(sb);
            return sb.toString();
        }
        return text.toString();
}
Replaces every subsequence of the input sequence that matches the
pattern with the given replacement string.

 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.  
 public String replaceFirst(String replacement) {
        if (replacement == null)
            throw new NullPointerException("replacement");
        reset();
        if (!find())
            return text.toString();
        StringBuffer sb = new StringBuffer();
        appendReplacement(sb, replacement);
        appendTail(sb);
        return sb.toString();
}
Replaces the first subsequence of the input sequence that matches the
pattern with the given 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  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.  
 public boolean requireEnd() {
        return requireEnd;
}
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.
 public Matcher reset() {
        first = -1;
        last = 0;
        oldLast = -1;
        for(int i=0; i< groups.length; i++)
            groups[i] = -1;
        for(int i=0; i< locals.length; i++)
            locals[i] = -1;
        lastAppendPosition = 0;
        from = 0;
        to = getTextLength();
        return this;
}
Resets this matcher.

 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.
 public Matcher reset(CharSequence input) {
        text = input;
        return reset();
}
Resets this matcher with a new input sequence.

 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.
 boolean search(int from) {
        this.hitEnd = false;
        this.requireEnd = false;
        from        = from <  0 ? 0 : from;
        this.first  = from;
        this.oldLast = oldLast <  0 ? from : oldLast;
        for (int i = 0; i <  groups.length; i++)
            groups[i] = -1;
        acceptMode = NOANCHOR;
        boolean result = parentPattern.root.match(this, from, text);
        if (!result)
            this.first = -1;
        this.oldLast = this.last;
        return result;
}
Initiates a search to find a Pattern within the given bounds.
The groups are filled with default values and the match of the root
of the state machine is called. The state machine will hold the state
of the match as it proceeds in this matcher.

Matcher.from is not set here, because it is the "hard" boundary
of the start of the search which anchors will set to. The from param
is the "soft" boundary of the start of the search, meaning that the
regex tries to match at that index but ^ won't match there. Subsequent
calls to the search methods start at a new "soft" boundary which is
the end of the previous match.
 public int start() {
        if (first <  0)
            throw new IllegalStateException("No match available");
        return first;
}
Returns the start index of the previous match.  
 public int start(int group) {
        if (first <  0)
            throw new IllegalStateException("No match available");
        if (group  > groupCount())
            throw new IndexOutOfBoundsException("No group " + group);
        return groups[group * 2];
}
Returns the start index of the subsequence captured by the given group
during the previous match operation.

 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().  
 public MatchResult toMatchResult() {
        Matcher result = new Matcher(this.parentPattern, text.toString());
        result.first = this.first;
        result.last = this.last;
        result.groups = this.groups.clone();
        return result;
}
Returns the match state of this matcher as a MatchResult .
The result is unaffected by subsequent operations performed upon this
matcher.
 public String toString() {
        StringBuilder sb = new StringBuilder();
        sb.append("java.util.regex.Matcher");
        sb.append("[pattern=" + pattern());
        sb.append(" region=");
        sb.append(regionStart() + "," + regionEnd());
        sb.append(" lastmatch=");
        if ((first  >= 0) && (group() != null)) {
            sb.append(group());
        }
        sb.append("]");
        return sb.toString();
}
Returns the string representation of this matcher. The
string representation of a Matcher contains information
that may be useful for debugging. The exact format is unspecified.
 public Matcher useAnchoringBounds(boolean b) {
        anchoringBounds = b;
        return this;
}
Sets the anchoring of region bounds for this matcher.

 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.
 public Matcher usePattern(Pattern newPattern) {
        if (newPattern == null)
            throw new IllegalArgumentException("Pattern cannot be null");
        parentPattern = newPattern;
        // Reallocate state storage
        int parentGroupCount = Math.max(newPattern.capturingGroupCount, 10);
        groups = new int[parentGroupCount * 2];
        locals = new int[newPattern.localCount];
        for (int i = 0; i <  groups.length; i++)
            groups[i] = -1;
        for (int i = 0; i <  locals.length; i++)
            locals[i] = -1;
        return this;
}
Changes the Pattern that this Matcher uses to
find matches with.

 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.
 public Matcher useTransparentBounds(boolean b) {
        transparentBounds = b;
        return this;
}
Sets the transparency of region bounds for this matcher.

 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.

Field Summary
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 $.