Matcher replaceFirst(String) Method in Java with Examples
Last Updated :
11 Jul, 2025
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The replaceFirst() method of Matcher Class behaves as an append-and-replace method. This method reads the input string and replaces it with the first matched pattern in the matcher string.
Syntax:
public String replaceFirst(String stringToBeReplaced)
Parameters: The string to be replaced that is the String to be replaced in the matcher.
Return Type: A string with the target string constructed by replacing the string.
Example 1:
// Java Program to Illustrate replaceFirst() Method
// of Matcher class
// Importing required classes
import java.util.regex.*;
// Main class
public class GFG {
// Main driver method
public static void main(String[] args)
{
// Getting the regex to be checked
String regex = "(Geeks)";
// Creating a pattern from regex
Pattern pattern = Pattern.compile(regex);
// Getting the String to be matched
String stringToBeMatched
= "GeeksForGeeks Geeks for For Geeks Geek";
// Creating a matcher for the input String
Matcher matcher
= pattern.matcher(stringToBeMatched);
// Displaying the string to be matched
// before replacing
System.out.println("Before Replacement: "
+ stringToBeMatched);
// Getting the string to be replaced
String stringToBeReplaced = "GFG";
StringBuilder builder = new StringBuilder();
// Replacing every matched pattern with the target
// string using replaceFirst() method
System.out.println(
"After Replacement: "
+ matcher.replaceFirst(stringToBeReplaced));
}
}
Output:
Before Replacement: GeeksForGeeks Geeks for For Geeks Geek After Replacement: GFGForGeeks Geeks for For Geeks Geek
Example 2:
// Java Program to Illustrate replaceFirst() Method
// Importing required classes
import java.util.regex.*;
// Main class
public class GFG {
// Main driver method
public static void main(String[] args)
{
// Getting the regex to be checked
String regex = "(FGF)";
// Creating a pattern from regex
Pattern pattern = Pattern.compile(regex);
// Getting the string to be matched
String stringToBeMatched = "FGF FGF FGF FGF";
// Creating a matcher for the input String
Matcher matcher
= pattern.matcher(stringToBeMatched);
// Printing string on console
// before replacement
System.out.println("Before Replacement: "
+ stringToBeMatched);
// Getting the string to be replaced
String stringToBeReplaced = "GFG";
StringBuilder builder = new StringBuilder();
// Replacing every matched pattern with target
// string using replaceFirst() method and printing
// the string to be replaced
System.out.println(
"After Replacement: "
+ matcher.replaceFirst(stringToBeReplaced));
}
}
Output:
Before Replacement: FGF FGF FGF FGF After Replacement: GFG FGF FGF FGF
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