Matcher appendTail(StringBuilder) method in Java with Examples

The appendTail(StringBuilder) method of Matcher Class behaves as a append-and-replace method. This method reads the input string and appends it to the given StringBuilder at the tail position.

Syntax:

public StringBuilder appendTail(StringBuilder builder)

Parameters: This method takes a parameter builder which is the StringBuilder that stores the target string.

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

Below examples illustrate the Matcher.appendTail() method:

Example 1:

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// Java code to illustrate appendTail() 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
        while (matcher.find()) {
            matcher
                .appendReplacement(builder,
                                   stringToBeReplaced);
        }
  
        // Add the replaced string at the tail
        // using the appendTail() method
        matcher.appendTail(builder);
  
        // Print the replaced matcher
        System.out.println("After Replacement: "
                           + builder.toString());
    }
}

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Output:

Before Replacement: GeeksForGeeks Geeks for For Geeks Geek
After Replacement: GFGForGFG GFG for For GFG Geek

Example 2:

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

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Output:

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

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



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