javautilregexMatcher

java.util.regex.Matcher is the runtime engine used to perform regex operations against a character sequence according to a compiled Pattern. A Matcher is created by Pattern.compile(regex).matcher(input) and the same Pattern can produce multiple Matcher instances. The Matcher maintains state about the current input region, the results of the last match, and any captured groups.

Key operations include find(), which searches for the next subsequence that matches the pattern; matches(), which attempts to match the entire region; and lookingAt(), which attempts to match from the region’s start. After a successful match, group(), group(int), and groupCount() provide access to captured substrings, with group(0) representing the entire match. start() and end() report the bounds of the overall match or of a specific group.

Region and boundaries can be controlled with region(int start, int end) to limit the search, and find(int start) to restart searching from a given position. Replacement and construction utilities include replaceAll(String) and replaceFirst(String) for producing a new string with substitutions, as well as appendReplacement and appendTail for incremental result building.

Additional features include reset() to reuse the same Matcher with a new input, and toMatchResult() to obtain a read-only view of the current match. Note that Matcher is not thread-safe; it should not be shared across threads.

See also Pattern and the java.util.regex package for related classes and utilities. Example usage typically involves compiling a Pattern, obtaining a Matcher for an input, iterating with find(), and retrieving groups as needed.