Matcher replaceFirst(String) method in Java with Examples

The replaceFirst(String) method of Matcher Class behaves as a append-and-replace method. This method reads the input string and replace it with the first matched pattern in the matcher string.

Syntax:

public String replaceFirst(String stringToBeReplaced)

Parameters: This method takes a parameter stringToBeReplaced which is the String to be replaced in the matcher.

Return Value: This method returns a String with the target String constructed by replacing the String.

Below examples illustrate the Matcher.replaceFirst() method:



Example 1:

filter_none

edit
close

play_arrow

link
brightness_4
code

// Java code to illustrate replaceFirst() method
  
import java.util.regex.*;
  
public class GFG {
    public static void main(String[] args)
    {
  
        // Get the regex to be checked
        String regex = "(Geeks)";
  
        // Create a pattern from regex
        Pattern pattern = Pattern.compile(regex);
  
        // Get the String to be matched
        String stringToBeMatched
            = "GeeksForGeeks Geeks for For Geeks Geek";
  
        // Create a matcher for the input String
        Matcher matcher
            = pattern.matcher(stringToBeMatched);
  
        System.out.println("Before Replacement: "
                           + stringToBeMatched);
  
        // Get the String to be replaced
        String stringToBeReplaced = "GFG";
        StringBuilder builder = new StringBuilder();
  
        // Replace every matched pattern
        // with the target String
        // using replaceFirst() method
        System.out.println("After Replacement: "
                           + matcher
                                 .replaceFirst(stringToBeReplaced));
    }
}

chevron_right


Output:

Before Replacement: GeeksForGeeks Geeks for For Geeks Geek
After Replacement: GFGForGeeks Geeks for For Geeks Geek

Example 2:

filter_none

edit
close

play_arrow

link
brightness_4
code

// Java code to illustrate replaceFirst() method
  
import java.util.regex.*;
  
public class GFG {
    public static void main(String[] args)
    {
  
        // Get the regex to be checked
        String regex = "(FGF)";
  
        // Create a pattern from regex
        Pattern pattern
            = Pattern.compile(regex);
  
        // Get the String to be matched
        String stringToBeMatched
            = "FGF FGF FGF FGF";
  
        // Create a matcher for the input String
        Matcher matcher
            = pattern.matcher(stringToBeMatched);
  
        System.out.println("Before Replacement: "
                           + stringToBeMatched);
  
        // Get the String to be replaced
        String stringToBeReplaced = "GFG";
        StringBuilder builder
            = new StringBuilder();
  
        // Replace every matched pattern
        // with the target String
        // using replaceFirst() method
        System.out.println("After Replacement: "
                           + matcher
                                 .replaceFirst(stringToBeReplaced));
    }
}

chevron_right


Output:

Before Replacement: FGF FGF FGF FGF
After Replacement: GFG FGF FGF FGF

Reference: https://docs.oracle.com/javase/9/docs/api/java/util/regex/Matcher.html#replaceFirst-java.lang.String-

Attention reader! Don’t stop learning now. Get hold of all the important Java and Collections concepts with the Fundamentals of Java and Java Collections Course at a student-friendly price and become industry ready.




My Personal Notes arrow_drop_up

Check out this Author's contributed articles.

If you like GeeksforGeeks and would like to contribute, you can also write an article using contribute.geeksforgeeks.org or mail your article to contribute@geeksforgeeks.org. See your article appearing on the GeeksforGeeks main page and help other Geeks.

Please Improve this article if you find anything incorrect by clicking on the "Improve Article" button below.



Improved By : Akanksha_Rai