MatchResult (Java SE 17 & JDK 17)
Description: declaration: module: java.base, package: java.util.regex, interface: MatchResult
Keywords: java.util.regex.MatchResult interface

Module java.base
Package java.util.regex

# Interface MatchResult

All Known Implementing Classes:
  `Matcher`

public interface MatchResult
The result of a match operation.

This interface contains query methods used to determine the results of a match against a regular expression. The match boundaries, groups and group boundaries can be seen but not modified through a `MatchResult`.

Since:
  1.5
See Also:
  - `Matcher`

- ## Method Summary

  Modifier and Type
  Method
  Description
  `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 this match.
  `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.
  `int`
  `groupCount()`
  Returns the number of capturing groups in this match result's pattern.
  `int`
  `start()`
  Returns the start index of the match.
  `int`
  `start(int group)`
  Returns the start index of the subsequence captured by the given group during this match.

- ## Method Details

  - ### start

    int start()
    Returns the start index of the match.
    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

    int start(int group)
    Returns the start index of the subsequence captured by the given group during this match.

    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()`.

    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

  - ### end

    int end()
    Returns the offset after the last character matched.
    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

    int end(int group)
    Returns the offset after the last character of the subsequence captured by the given group during this match.

    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()`.

    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

  - ### group

    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.

    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

    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.

    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

  - ### groupCount

    int groupCount()
    Returns the number of capturing groups in this match result'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.

    Returns:
      The number of capturing groups in this matcher's pattern