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Matcher Class in Java

Last Updated : 27 Jan, 2026

Regular Expressions in Java provide a way to match, search, and manipulate text. The Matcher class is part of the java.util.regex package is used to perform matching operations on an input string using a compiled regular expression (Pattern). The Matcher class provides methods to:

  • Check matches
  • Retrieve match positions
  • Study the matching state
  • Replace matched content

Output
true

Explanation:

  • Pattern.compile("java") creates a regex pattern to search for the word "java".
  • matcher.find() checks whether the pattern occurs anywhere in the string "java is java", so it returns true.

Methods of Matcher class:

1. Match Methods

Match methods are used to check whether a pattern matches the input string, either completely or partially.

Method

Description

matches()

Checks if the entire input matches the pattern

find()

Finds the next occurrence of the pattern

lookingAt()

Checks if the pattern matches from the beginning

Example: Difference between matches(), lookingAt(), and find()


Output
false
true
Match found

Explanation:

  • matches() fails because the entire string is not exactly "java"
  • lookingAt() succeeds as the string starts with "java"
  • find() locates each occurrence of "java"
  • find() can be called multiple times
  • Matching state is maintained internally

2. Index Methods

Index methods return positional information about the current match in the input string.

Method NameDescription
start()returns the start index of the previous match.
start(int group)returns the start index of the subsequence captured by the given group during the previous match operation.
end()returns the offset after the last character is matched.
end(int group)returns the offset after the last character of the subsequence captured by the given group during the previous match operation.

Example: Retrieving match positions using index methods


Output
7
11
7
11

Explanation:

  • find() locates the match
  • start() returns the index where the match begins
  • end() returns the index after the match ends
  • Group-based methods return positions of captured groups
  • Indexing is zero-based

3. Study Methods

Study methods are used to inspect the state and behavior of the matcher during pattern matching.

Method NameDescription
groupCount()Returns number of capturing groups
group()Returns the matched substring
hitEnd()Checks if match reached end of input
requireEnd()Checks if more input could change the result

Example: Inspecting matcher state using study methods


Output
java5
2
false
false

Explanation:

  • group() returns the complete match
  • groupCount() returns number of capturing groups
  • hitEnd() checks if matcher reached input end
  • requireEnd() checks if more input may affect the match
  • Useful in stream-based matching

4. Replacement Methods: 

Replacement methods are used to modify the input string based on regex matches.

Method NameDescription
appendReplacement(StringBuffer sb, String replacement)Performs a non-terminal append-and-replace operation.
appendTail(StringBuffer sb)Appends the remaining input after the last match.
replaceAll(String replacement)Replaces all matching subsequences.
replaceFirst(String replacement)Replaces the first matching subsequence.

Example: Replacing matched text using Matcher methods


Output
Java is java
Java is Java
Java is Java

Explanation:

  • replaceFirst() replaces only the first match
  • replaceAll() replaces every match
  • appendReplacement() builds result incrementally
  • appendTail() appends remaining text
  • Maintains original string structure
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