Matcher replaceFirst(String) Method in Java with Examples

Last Updated : 10 Nov, 2021

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

// 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

// 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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Kirti_Mangal

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