Matcher.appendReplacement example – Part 2

In this example we shall show you how to use Matcher.appendReplacement(StringBuffer sb, String replacement) API method to append to a StringBuffer the result of a Matcher. To use a StringBuffer to append a Matcher’s result one should perform the following steps:

  • Compile a given String regular expression to a Pattern, using compile(string regex) API method of Pattern.
  • Use matcher(CharSequence input) API method of Pattern to create a Matcher that will match the given String input against this pattern.
  • Create a new StringBuffer.
  • While the matcher finds the next subsequence of the input sequence that matches the pattern, with find() API method of Matcher get the input subsequence matched, with group() API method of Matcher and append it to the StringBuffer, implementing a non-terminal append-and-replace step, using appendReplacement(StringBuffer sb, String replacement) API method of Matcher.
  • Then use appendTail(StringBuffer sb) API method of Matcher to implement a terminal append-and-replace step and print the result from the StringBuffer,

as described in the code snippet below.

package com.javacodegeeks.snippets.core;

import java.util.regex.Matcher;
import java.util.regex.Pattern;

public class AppendRepl {

    public static void main(String[] argv) throws Exception {

  CharSequence input = "ab12 cd efg34 asdf 123";

  String pattStr = "([a-zA-Z]+[0-9]+)";

  Pattern p = Pattern.compile(pattStr);

  Matcher m = p.matcher(input);

  StringBuffer bufStr = new StringBuffer();


  boolean flag = false;


  while ((flag = m.find())) {

String rep =;

m.appendReplacement(bufStr, "found<" + rep + ">");



  String result = bufStr.toString();



found<ab12> cd found<efg34> asdf 123

This was an example of how to Matcher.appendReplacement(StringBuffer sb, String replacement) API method in Java.

Byron Kiourtzoglou

Byron is a master software engineer working in the IT and Telecom domains. He is an applications developer in a wide variety of applications/services. He is currently acting as the team leader and technical architect for a proprietary service creation and integration platform for both the IT and Telecom industries in addition to a in-house big data real-time analytics solution. He is always fascinated by SOA, middleware services and mobile development. Byron is co-founder and Executive Editor at Java Code Geeks.
Notify of

This site uses Akismet to reduce spam. Learn how your comment data is processed.

Inline Feedbacks
View all comments
Back to top button