Module java.base
Package java.util.regex

Class Matcher

java.lang.Object
java.util.regex.Matcher
All Implemented Interfaces:
MatchResult
public final class Matcher extends Object implements 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 string builder. Alternatively, 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.

Since:
1.4

  • Method Summary

    Modifier and Type
    Method
    Description
    Matcher
    appendReplacement(StringBuffer sb, String replacement)
    Implements a non-terminal append-and-replace step.
    Matcher
    appendReplacement(StringBuilder sb, String replacement)
    Implements a non-terminal append-and-replace step.
    StringBuffer
    appendTail(StringBuffer sb)
    Implements a terminal append-and-replace step.
    StringBuilder
    appendTail(StringBuilder sb)
    Implements a terminal append-and-replace step.
    int
    end()
    Returns the offset after the last character matched.
    int
    end(int group)
    Returns the offset after the last character of the subsequence captured by the given group during the previous match operation.
    int
    end(String name)
    Returns the offset after the last character of the subsequence captured by the given named-capturing group during the previous match operation.
    boolean
    find()
    Attempts to find the next subsequence of the input sequence that matches the pattern.
    boolean
    find(int 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.
    String
    group()
    Returns the input subsequence matched by the previous match.
    String
    group(int group)
    Returns the input subsequence captured by the given group during the previous match operation.
    String
    group(String name)
    Returns the input subsequence captured by the given named-capturing group during the previous match operation.
    int
    groupCount()
    Returns the number of capturing groups in this matcher's pattern.
    boolean
    hasAnchoringBounds()
    Queries the anchoring of region bounds for this matcher.
    boolean
    hasMatch()
    Returns whether this contains a valid match from a previous match or find operation.
    boolean
    hasTransparentBounds()
    Queries the transparency of region bounds for this matcher.
    boolean
    hitEnd()
    Returns true if the end of input was hit by the search engine in the last match operation performed by this matcher.
    boolean
    lookingAt()
    Attempts to match the input sequence, starting at the beginning of the region, against the pattern.
    boolean
    matches()
    Attempts to match the entire region against the pattern.
    Map<String,Integer>
    namedGroups()
    Returns an unmodifiable map from capturing group names to group numbers.
    Pattern
    pattern()
    Returns the pattern that is interpreted by this matcher.
    static String
    quoteReplacement(String s)
    Returns a literal replacement String for the specified String.
    Matcher
    region(int start, int end)
    Sets the limits of this matcher's region.
    int
    regionEnd()
    Reports the end index (exclusive) of this matcher's region.
    int
    regionStart()
    Reports the start index of this matcher's region.
    String
    replaceAll(String replacement)
    Replaces every subsequence of the input sequence that matches the pattern with the given replacement string.
    String
    replaceAll(Function<MatchResult,String> replacer)
    Replaces every subsequence of the input sequence that matches the pattern with the result of applying the given replacer function to the match result of this matcher corresponding to that subsequence.
    String
    replaceFirst(String replacement)
    Replaces the first subsequence of the input sequence that matches the pattern with the given replacement string.
    String
    replaceFirst(Function<MatchResult,String> replacer)
    Replaces the first subsequence of the input sequence that matches the pattern with the result of applying the given replacer function to the match result of this matcher corresponding to that subsequence.
    boolean
    requireEnd()
    Returns true if more input could change a positive match into a negative one.
    Matcher
    reset()
    Resets this matcher.
    Matcher
    reset(CharSequence input)
    Resets this matcher with a new input sequence.
    Stream<MatchResult>
    results()
    Returns a stream of match results for each subsequence of the input sequence that matches the pattern.
    int
    start()
    Returns the start index of the previous match.
    int
    start(int group)
    Returns the start index of the subsequence captured by the given group during the previous match operation.
    int
    start(String name)
    Returns the start index of the subsequence captured by the given named-capturing group during the previous match operation.
    MatchResult
    toMatchResult()
    Returns the match state of this matcher as a MatchResult.
    String
    toString()
    Returns the string representation of this matcher.
    Matcher
    useAnchoringBounds(boolean b)
    Sets the anchoring of region bounds for this matcher.
    Matcher
    usePattern(Pattern newPattern)
    Changes the Pattern that this Matcher uses to find matches with.
    Matcher
    useTransparentBounds(boolean b)
    Sets the transparency of region bounds for this matcher.

    Methods declared in class java.lang.Object

    clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

  • Method Details

    • pattern

      public Pattern pattern()
      Returns the pattern that is interpreted by this matcher.
      Returns:
      The pattern for which this matcher was created

    • toMatchResult

      public MatchResult toMatchResult()
      Returns the match state of this matcher as a MatchResult. The result is unaffected by subsequent operations performed upon this matcher.
      Returns:
      a MatchResult with the state of this matcher
      Since:
      1.5

    • usePattern

      public Matcher usePattern(Pattern newPattern)
      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.

      Parameters:
      newPattern - The new pattern used by this matcher
      Returns:
      This matcher
      Throws:
      IllegalArgumentException - If newPattern is null
      Since:
      1.5

    • reset

      public Matcher reset()
      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.

      Returns:
      This matcher

    • reset

      public Matcher reset(CharSequence input)
      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.

      Parameters:
      input - The new input character sequence
      Returns:
      This matcher

    • start

      public int start()
      Returns the start index of the previous match.
      Specified by:
      start in interface MatchResult
      Returns:
      The index of the first character matched
      Throws:
      IllegalStateException - If no match has yet been attempted, or if the previous match operation failed

    • start

      public int start(int group)
      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().

      Specified by:
      start in interface MatchResult
      Parameters:
      group - The index of a capturing group in this matcher's pattern
      Returns:
      The index of the first character captured by the group, or -1 if the match was successful but the group itself did not match anything
      Throws:
      IllegalStateException - If no match has yet been attempted, or if the previous match operation failed
      IndexOutOfBoundsException - If there is no capturing group in the pattern with the given index

    • start

      public int start(String name)
      Returns the start index of the subsequence captured by the given named-capturing group during the previous match operation.
      Specified by:
      start in interface MatchResult
      Parameters:
      name - The name of a named-capturing group in this matcher's pattern
      Returns:
      The index of the first character captured by the group, or -1 if the match was successful but the group itself did not match anything
      Throws:
      IllegalStateException - If no match has yet been attempted, or if the previous match operation failed
      IllegalArgumentException - If there is no capturing group in the pattern with the given name
      Since:
      1.8

    • end

      public int end()
      Returns the offset after the last character matched.
      Specified by:
      end in interface MatchResult
      Returns:
      The offset after the last character matched
      Throws:
      IllegalStateException - If no match has yet been attempted, or if the previous match operation failed

    • end

      public int end(int group)
      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().

      Specified by:
      end in interface MatchResult
      Parameters:
      group - The index of a capturing group in this matcher's pattern
      Returns:
      The offset after the last character captured by the group, or -1 if the match was successful but the group itself did not match anything
      Throws:
      IllegalStateException - If no match has yet been attempted, or if the previous match operation failed
      IndexOutOfBoundsException - If there is no capturing group in the pattern with the given index

    • end

      public int end(String name)
      Returns the offset after the last character of the subsequence captured by the given named-capturing group during the previous match operation.
      Specified by:
      end in interface MatchResult
      Parameters:
      name - The name of a named-capturing group in this matcher's pattern
      Returns:
      The offset after the last character captured by the group, or -1 if the match was successful but the group itself did not match anything
      Throws:
      IllegalStateException - If no match has yet been attempted, or if the previous match operation failed
      IllegalArgumentException - If there is no capturing group in the pattern with the given name
      Since:
      1.8

    • group

      public String group()
      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.

      Specified by:
      group in interface MatchResult
      Returns:
      The (possibly empty) subsequence matched by the previous match, in string form
      Throws:
      IllegalStateException - If no match has yet been attempted, or if the previous match operation failed

    • group

      public String group(int group)
      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.

      Specified by:
      group in interface MatchResult
      Parameters:
      group - The index of a capturing group in this matcher's pattern
      Returns:
      The (possibly empty) subsequence captured by the group during the previous match, or null if the group failed to match part of the input
      Throws:
      IllegalStateException - If no match has yet been attempted, or if the previous match operation failed
      IndexOutOfBoundsException - If there is no capturing group in the pattern with the given index

    • group

      public String group(String name)
      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.

      Specified by:
      group in interface MatchResult
      Parameters:
      name - The name of a named-capturing group in this matcher's pattern
      Returns:
      The (possibly empty) subsequence captured by the named group during the previous match, or null if the group failed to match part of the input
      Throws:
      IllegalStateException - If no match has yet been attempted, or if the previous match operation failed
      IllegalArgumentException - If there is no capturing group in the pattern with the given name
      Since:
      1.7

    • groupCount

      public int groupCount()
      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.

      Specified by:
      groupCount in interface MatchResult
      Returns:
      The number of capturing groups in this matcher's pattern

    • matches

      public boolean matches()
      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.

      Returns:
      true if, and only if, the entire region sequence matches this matcher's pattern

    • find

      public boolean find()
      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.

      Returns:
      true if, and only if, a subsequence of the input sequence matches this matcher's pattern

    • find

      public boolean find(int 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.

      Parameters:
      start - the index to start searching for a match
      Returns:
      true if, and only if, a subsequence of the input sequence starting at the given index matches this matcher's pattern
      Throws:
      IndexOutOfBoundsException - If start is less than zero or if start is greater than the length of the input sequence.

    • lookingAt

      public boolean lookingAt()
      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.

      Returns:
      true if, and only if, a prefix of the input sequence matches this matcher's pattern

    • quoteReplacement

      public static String quoteReplacement(String s)
      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.
      Parameters:
      s - The string to be literalized
      Returns:
      A literal string replacement
      Since:
      1.5

    • appendReplacement

      public Matcher appendReplacement(StringBuffer sb, String replacement)
      Implements a non-terminal append-and-replace step.

      This method performs the following actions:

      1. 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.

      2. It appends the given replacement string to the string buffer.

      3. 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());
      Parameters:
      sb - The target string buffer
      replacement - The replacement string
      Returns:
      This matcher
      Throws:
      IllegalStateException - If no match has yet been attempted, or if the previous match operation failed
      IllegalArgumentException - If the replacement string refers to a named-capturing group that does not exist in the pattern
      IndexOutOfBoundsException - If the replacement string refers to a capturing group that does not exist in the pattern

    • appendReplacement

      public Matcher appendReplacement(StringBuilder sb, String replacement)
      Implements a non-terminal append-and-replace step.

      This method performs the following actions:

      1. It reads characters from the input sequence, starting at the append position, and appends them to the given string builder. It stops after reading the last character preceding the previous match, that is, the character at index start() - 1.

      2. It appends the given replacement string to the string builder.

      3. 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 "$2bar" would cause "foobar" to be appended to the string builder. A dollar sign ($) 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");
 StringBuilder sb = new StringBuilder();
 while (m.find()) {
     m.appendReplacement(sb, "dog");
 }
 m.appendTail(sb);
 System.out.println(sb.toString());
      Parameters:
      sb - The target string builder
      replacement - The replacement string
      Returns:
      This matcher
      Throws:
      IllegalStateException - If no match has yet been attempted, or if the previous match operation failed
      IllegalArgumentException - If the replacement string refers to a named-capturing group that does not exist in the pattern
      IndexOutOfBoundsException - If the replacement string refers to a capturing group that does not exist in the pattern
      Since:
      9

    • appendTail

      public StringBuffer appendTail(StringBuffer 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.

      Parameters:
      sb - The target string buffer
      Returns:
      The target string buffer

    • appendTail

      public StringBuilder appendTail(StringBuilder 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 builder. 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.

      Parameters:
      sb - The target string builder
      Returns:
      The target string builder
      Since:
      9

    • replaceAll

      public String replaceAll(String replacement)
      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.

      Parameters:
      replacement - The replacement string
      Returns:
      The string constructed by replacing each matching subsequence by the replacement string, substituting captured subsequences as needed

    • replaceAll

      public String replaceAll(Function<MatchResult,String> replacer)
      Replaces every subsequence of the input sequence that matches the pattern with the result of applying the given replacer function to the match result of this matcher corresponding to that subsequence. Exceptions thrown by the function are relayed to the caller.

      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 applying the replacer function that returns a replacement string. Each replacement string may contain references to captured subsequences as in the appendReplacement method.

      Note that backslashes (\) and dollar signs ($) in a 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 function mr -> mr.group().toUpperCase(), an invocation of this method on a matcher for that expression would yield the string "zzzDOGzzzDOGzzz".

      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.

      The replacer function should not modify this matcher's state during replacement. This method will, on a best-effort basis, throw a ConcurrentModificationException if such modification is detected.

      The state of each match result passed to the replacer function is guaranteed to be constant only for the duration of the replacer function call and only if the replacer function does not modify this matcher's state.

      Implementation Note:
      This implementation applies the replacer function to this matcher, which is an instance of MatchResult.
      Parameters:
      replacer - The function to be applied to the match result of this matcher that returns a replacement string.
      Returns:
      The string constructed by replacing each matching subsequence with the result of applying the replacer function to that matched subsequence, substituting captured subsequences as needed.
      Throws:
      NullPointerException - if the replacer function is null
      ConcurrentModificationException - if it is detected, on a best-effort basis, that the replacer function modified this matcher's state
      Since:
      9

    • results

      public Stream<MatchResult> results()
      Returns a stream of match results for each subsequence of the input sequence that matches the pattern. The match results occur in the same order as the matching subsequences in the input sequence.

      Each match result is produced as if by toMatchResult().

      This method does not reset this matcher. Matching starts on initiation of the terminal stream operation either at the beginning of this matcher's region, or, if the matcher has not since been reset, at the first character not matched by a previous match.

      If the matcher is to be used for further matching operations after the terminal stream operation completes then it should be first reset.

      This matcher's state should not be modified during execution of the returned stream's pipeline. The returned stream's source Spliterator is fail-fast and will, on a best-effort basis, throw a ConcurrentModificationException if such modification is detected.

      Returns:
      a sequential stream of match results.
      Since:
      9

    • replaceFirst

      public String replaceFirst(String replacement)
      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.

      Parameters:
      replacement - The replacement string
      Returns:
      The string constructed by replacing the first matching subsequence by the replacement string, substituting captured subsequences as needed

    • replaceFirst

      public String replaceFirst(Function<MatchResult,String> replacer)
      Replaces the first subsequence of the input sequence that matches the pattern with the result of applying the given replacer function to the match result of this matcher corresponding to that subsequence. Exceptions thrown by the replace function are relayed to the caller.

      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 applying the replacer function that returns a 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 function mr -> mr.group().toUpperCase(), an invocation of this method on a matcher for that expression would yield the string "zzzDOGzzzdogzzz".

      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.

      The replacer function should not modify this matcher's state during replacement. This method will, on a best-effort basis, throw a ConcurrentModificationException if such modification is detected.

      The state of the match result passed to the replacer function is guaranteed to be constant only for the duration of the replacer function call and only if the replacer function does not modify this matcher's state.

      Implementation Note:
      This implementation applies the replacer function to this matcher, which is an instance of MatchResult.
      Parameters:
      replacer - The function to be applied to the match result of this matcher that returns a replacement string.
      Returns:
      The string constructed by replacing the first matching subsequence with the result of applying the replacer function to the matched subsequence, substituting captured subsequences as needed.
      Throws:
      NullPointerException - if the replacer function is null
      ConcurrentModificationException - if it is detected, on a best-effort basis, that the replacer function modified this matcher's state
      Since:
      9

    • region

      public Matcher region(int start, int end)
      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.

      Parameters:
      start - The index to start searching at (inclusive)
      end - The index to end searching at (exclusive)
      Returns:
      this matcher
      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.
      Since:
      1.5

    • regionStart

      public int regionStart()
      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).
      Returns:
      The starting point of this matcher's region
      Since:
      1.5

    • regionEnd

      public int regionEnd()
      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).
      Returns:
      the ending point of this matcher's region
      Since:
      1.5

    • hasTransparentBounds

      public boolean hasTransparentBounds()
      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.

      Returns:
      true iff this matcher is using transparent bounds, false otherwise.
      Since:
      1.5
      See Also:

    • useTransparentBounds

      public Matcher useTransparentBounds(boolean b)
      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.

      Parameters:
      b - a boolean indicating whether to use opaque or transparent regions
      Returns:
      this matcher
      Since:
      1.5
      See Also:

    • hasAnchoringBounds

      public boolean hasAnchoringBounds()
      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.

      Returns:
      true iff this matcher is using anchoring bounds, false otherwise.
      Since:
      1.5
      See Also:

    • useAnchoringBounds

      public Matcher useAnchoringBounds(boolean b)
      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.

      Parameters:
      b - a boolean indicating whether or not to use anchoring bounds.
      Returns:
      this matcher
      Since:
      1.5
      See Also:

    • toString

      public String 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.

      Overrides:
      toString in class Object
      Returns:
      The string representation of this matcher
      Since:
      1.5

    • hitEnd

      public boolean 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.

      Returns:
      true iff the end of input was hit in the last match; false otherwise
      Since:
      1.5

    • requireEnd

      public boolean 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.

      Returns:
      true iff more input could change a positive match into a negative one.
      Since:
      1.5

    • namedGroups

      public Map<String,Integer> namedGroups()
      Returns an unmodifiable map from capturing group names to group numbers. If there are no named groups, returns an empty map.
      Specified by:
      namedGroups in interface MatchResult
      Returns:
      an unmodifiable map from capturing group names to group numbers
      Since:
      20

    • hasMatch

      public boolean hasMatch()
      Returns whether this contains a valid match from a previous match or find operation.
      Specified by:
      hasMatch in interface MatchResult
      Returns:
      whether this contains a valid match
      Since:
      20