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Matcher appendTail(StringBuilder) method in Java with Examples

Last Updated : 27 Nov, 2018
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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: Java 
// 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());
    }
}
Output: 
Before Replacement: GeeksForGeeks Geeks for For Geeks Geek
After Replacement: GFGForGFG GFG for For GFG Geek
Example 2: Java 
// 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());
    }
}
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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Kirti_Mangal
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