Matcher appendReplacement(StringBuffer, String) method in Java with Examples

Last Updated : 27 Nov, 2018

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

Syntax:

public Matcher 
    appendReplacement(StringBuffer buffer, 
                      String stringToBeReplaced)

Parameters: This method takes two parameters:

buffer: which is the StringBuffer that stores the target string.
stringToBeReplaced: which is the String to be replaced in the matcher.

Return Value: This method returns a Matcher with the target String replaced.

Exception: This method throws following exceptions:

IllegalStateException: If no match has yet been attempted, or if the previous match operation failed
IllegalArgumentException: If the replacement string refers to a named-capturing group that does not exist in the pattern
IndexOutOfBoundsException: If the replacement string refers to a capturing group that does not exist in the pattern

Below examples illustrate the Matcher.appendReplacement() method:

Example 1:

// Java code to illustrate appendReplacement() 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 = "GEEKS"; 
        StringBuffer buffer = new StringBuffer(); 
  
        // Replace every matched pattern 
        // with the target String 
        // using appendReplacement() method 
        while (matcher.find()) { 
            matcher.appendReplacement(buffer, 
                                      stringToBeReplaced); 
        } 
        matcher.appendTail(buffer); 
  
        // Print the replaced matcher 
        System.out.println("After Replacement: "
                           + buffer.toString()); 
    } 
} 

Output:

Before Replacement: GeeksForGeeks Geeks for For Geeks Geek
After Replacement: GEEKSForGEEKS GEEKS for For GEEKS Geek

Example 2:

// Java code to illustrate appendReplacement() 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"; 
        StringBuffer buffer = new StringBuffer(); 
  
        // Replace every matched pattern 
        // with the target String 
        // using appendReplacement() method 
        while (matcher.find()) { 
            matcher.appendReplacement(buffer, 
                                      stringToBeReplaced); 
        } 
        matcher.appendTail(buffer); 
  
        // Print the replaced matcher 
        System.out.println("After Replacement: "
                           + buffer.toString()); 
    } 
} 

Output:

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

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

Matcher appendTail(StringBuffer) method in Java with Examples

Kirti_Mangal

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Matcher appendReplacement(StringBuffer, String) method in Java with Examples

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