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Matcher Class in Java - GeeksforGeeks

Last Updated : 16 Feb, 2022

In Java, Matcher is a class that is implemented by the MatchResult interface, that performs match operations on a character sequence by interpreting a Pattern.

Below, we can see the declaration of java.util.regex.Matcher in java.lang.Object Class:

public final class Matcher extends Object implements MatchResult

By invoking the pattern's matcher method, a matcher is created from a pattern. If a matcher is created once, we can perform three different kinds of match operations on it:

• matches(): Try to match the total input sequence against the pattern.
• lookingAt(): Try to match the input sequence, against the pattern, starting at the beginning.
• find(): This scans the input sequence and looks for the next subsequence especially matches the pattern.

Below the methods of the Matcher class are grouped in the table for convenience according to their functionality.

It provides useful index values. It shows precisely whether the match was found in the input string or not:

It reviews the input string and returns a boolean indicating whether the pattern is found or not:

These are useful methods for replacing text in an input string:

Example 1: Here we can see the example GFG.java which count the number of times the word "geek" appears in the input string using start()  and end() :

// Java program to demonstrate the
// methods of Matcher class in Java

import java.util.regex.Matcher;
import java.util.regex.Pattern;

public class GFG {

    private static final String REGEX = "\\bgeek\\b";
    private static final String INPUT
        = "geek geek geek geekie geeks";

    public static void main(String[] args)
    {
        Pattern pat = Pattern.compile(REGEX);
      
        //  here get a matcher object
        Matcher mat = pat.matcher(INPUT);
      
        // initialize a count variable to count
        int count = 0;

        // try to match the entire input sequence against
        // the pattern using the loop
        while (mat.find()) {
            count++;
            System.out.println("Match number " + count);
            System.out.println("start(): " + mat.start());
            System.out.println("end(): " + mat.end());
        }
    }
}

Match number 1
start(): 0
end(): 4
Match number 2
start(): 5
end(): 9
Match number 3
start(): 10
end(): 14

Example 2: In this example, we can see GFG.java, the lookingAt() and matches() both attempt to match an input sequence against a pattern.

// Java program to demonstrate the
// methods of Matcher class in Java

import java.util.regex.Matcher;
import java.util.regex.Pattern;

public class GFG {

    private static final String REGEX = "geek";
    private static final String INPUT = "geeksforgeeks";
    private static Pattern pat;
    private static Matcher mat;

    public static void main(String[] args)
    {

        // Initialization for pattern and matcher
        pat = Pattern.compile(REGEX);
        mat = pat.matcher(INPUT);

        System.out.println("Current REGEX: " + REGEX);
        System.out.println("Current INPUT: " + INPUT);

        System.out.println("lookingAt(): "
                           + mat.lookingAt());
        System.out.println("matches(): " + mat.matches());
    }
}

Current REGEX: geek
Current INPUT: geeksforgeeks
lookingAt(): true
matches(): false

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