A matcher is created from a pattern by invoking the pattern's {@link * Pattern#matcher matcher} method. Once created, a matcher can be used to * perform three different kinds of match operations: * *
The {@link #matches matches} method attempts to match the entire * input sequence against the pattern.
The {@link #lookingAt lookingAt} method attempts to match the * input sequence, starting at the beginning, against the pattern.
The {@link #find 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{@link #region region} method and queried * via the {@link #regionStart regionStart} and {@link #regionEnd regionEnd} * methods. The way that the region boundaries interact with some pattern * constructs can be changed. See {@link #useAnchoringBounds * useAnchoringBounds} and {@link #useTransparentBounds 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 {@link #appendReplacement appendReplacement} and {@link * #appendTail appendTail} methods can be used in tandem in order to collect * the result into an existing string buffer, or the more convenient {@link * #replaceAll 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 {@link * 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 {@link #appendReplacement appendReplacement} method. * *
A matcher may be reset explicitly by invoking its {@link #reset()} * method or, if a new input sequence is desired, its {@link * #reset(java.lang.CharSequence) 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 */ public final class Matcher implements MatchResult { /** * The Pattern object that created this Matcher. */ Pattern parentPattern; /** * The storage used by groups. They may contain invalid values if * a group was skipped during the matching. */ int[] groups; /** * The range within the sequence that is to be matched. Anchors * will match at these "hard" boundaries. Changing the region * changes these values. */ int from, to; /** * Lookbehind uses this value to ensure that the subexpression * match ends at the point where the lookbehind was encountered. */ int lookbehindTo; /** * The original string being matched. */ CharSequence text; /** * 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 ENDANCHOR = 1; static final int NOANCHOR = 0; int acceptMode = NOANCHOR; /** * 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 first = -1, last = 0; /** * The end index of what matched in the last match operation. */ int oldLast = -1; /** * The index of the last position appended in a substitution. */ int lastAppendPosition = 0; /** * 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. */ int[] locals; /** * 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 hitEnd; /** * 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 requireEnd; /** * 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 transparentBounds = false; /** * If anchoringBounds is true then the boundaries of this * matcher's region match anchors such as ^ and $. */ boolean anchoringBounds = true; /** * No default constructor. */ Matcher() { } /** * All matchers have the state used by Pattern during a match. */ 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(); } /** * Returns the pattern that is interpreted by this matcher. * * @return The pattern for which this matcher was created */ public Pattern pattern() { return parentPattern; } /** * Returns the match state of this matcher as a {@link MatchResult}. * The result is unaffected by subsequent operations performed upon this * matcher. * * @return aMatchResult with the state of this matcher
* @since 1.5
*/
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;
}
/**
* 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.
* * @param newPattern * The new pattern used by this matcher * @return This matcher * @throws IllegalArgumentException * If newPattern is null * @since 1.5 */ 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; } /** * 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.
*
* @return This matcher
*/
public Matcher reset() {
first = -1;
last = 0;
oldLast = -1;
for(int i=0; i 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(). 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(). 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. If the match succeeds then more information can be obtained via the
* start, end, and group methods. 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 {@link #find()} method will start at the first
* character not matched by this match. Like the {@link #matches 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 {@link 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.
*
* @param s The string to be literalized
* @return A literal string replacement
* @since 1.5
*/
public static String quoteReplacement(String s) {
if ((s.indexOf('\\') == -1) && (s.indexOf('$') == -1))
return s;
StringBuilder sb = new StringBuilder();
for (int i=0; i
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 {@link * #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 {@link #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 * {@link #group(String) group(name)} or {@link #group(int) 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 * {@link #appendTail appendTail} and {@link #find 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 {@link * #appendReplacement appendReplacement} method in order to copy the * remainder of the input sequence.
* * @param sb * The target string buffer * * @return The target string buffer */ public StringBuffer appendTail(StringBuffer sb) { sb.append(text, lastAppendPosition, getTextLength()); return sb; } /** * 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 {@link * #appendReplacement 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.
* * @param replacement * The replacement string * * @return The string constructed by replacing each matching subsequence * by the replacement string, substituting captured subsequences * as needed */ 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 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 {@link * #appendReplacement 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.
* * @param replacement * The replacement string * @return The string constructed by replacing the first matching * subsequence by the replacement string, substituting captured * subsequences as needed */ 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(); } /** * 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 thestart parameter and end at the
* index specified by the end parameter.
*
* Depending on the transparency and anchoring being used (see * {@link #useTransparentBounds useTransparentBounds} and * {@link #useAnchoringBounds useAnchoringBounds}), certain constructs such * as anchors may behave differently at or around the boundaries of the * region. * * @param start * The index to start searching at (inclusive) * @param end * The index to end searching at (exclusive) * @throws 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. * @return this matcher * @since 1.5 */ 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; } /** * Reports the start index of this matcher's region. The * searches this matcher conducts are limited to finding matches * within {@link #regionStart regionStart} (inclusive) and * {@link #regionEnd regionEnd} (exclusive). * * @return The starting point of this matcher's region * @since 1.5 */ public int regionStart() { return from; } /** * Reports the end index (exclusive) of this matcher's region. * The searches this matcher conducts are limited to finding matches * within {@link #regionStart regionStart} (inclusive) and * {@link #regionEnd regionEnd} (exclusive). * * @return the ending point of this matcher's region * @since 1.5 */ public int regionEnd() { return to; } /** * 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 {@link #useTransparentBounds useTransparentBounds} for a * description of transparent and opaque bounds. * *
By default, a matcher uses opaque region boundaries. * * @return true iff this matcher is using transparent bounds, * false otherwise. * @see java.util.regex.Matcher#useTransparentBounds(boolean) * @since 1.5 */ public boolean hasTransparentBounds() { return transparentBounds; } /** * 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. * * @param b a boolean indicating whether to use opaque or transparent * regions * @return this matcher * @see java.util.regex.Matcher#hasTransparentBounds * @since 1.5 */ public Matcher useTransparentBounds(boolean b) { transparentBounds = b; return this; } /** * Queries the anchoring of region bounds for this matcher. * *
This method returns true if this matcher uses * anchoring bounds, false otherwise. * *
See {@link #useAnchoringBounds useAnchoringBounds} for a * description of anchoring bounds. * *
By default, a matcher uses anchoring region boundaries. * * @return true iff this matcher is using anchoring bounds, * false otherwise. * @see java.util.regex.Matcher#useAnchoringBounds(boolean) * @since 1.5 */ public boolean hasAnchoringBounds() { return anchoringBounds; } /** * 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. * * @param b a boolean indicating whether or not to use anchoring bounds. * @return this matcher * @see java.util.regex.Matcher#hasAnchoringBounds * @since 1.5 */ public Matcher useAnchoringBounds(boolean b) { anchoringBounds = b; return this; } /** *
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.
*
* @return The string representation of this matcher
* @since 1.5
*/
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 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. * * @return true iff the end of input was hit in the last match; false * otherwise * @since 1.5 */ public boolean hitEnd() { return hitEnd; } /** *
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. * * @return true iff more input could change a positive match into a * negative one. * @since 1.5 */ public boolean requireEnd() { return requireEnd; } /** * 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. */ 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 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. */ 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; } /** * Returns the end index of the text. * * @return the index after the last character in the text */ int getTextLength() { return text.length(); } /** * Generates a String from this Matcher's input in the specified range. * * @param beginIndex the beginning index, inclusive * @param endIndex the ending index, exclusive * @return A String generated from this Matcher's input */ CharSequence getSubSequence(int beginIndex, int endIndex) { return text.subSequence(beginIndex, endIndex); } /** * Returns this Matcher's input character at index i. * * @return A char from the specified index */ char charAt(int i) { return text.charAt(i); } /** * Returns the group index of the matched capturing group. * * @return the index of the named-capturing group */ int getMatchedGroupIndex(String name) { Objects.requireNonNull(name, "Group name"); if (first < 0) throw new IllegalStateException("No match found"); if (!parentPattern.namedGroups().containsKey(name)) throw new IllegalArgumentException("No group with name <" + name + ">"); return parentPattern.namedGroups().get(name); } }