import java.util.regex.Matcher;
import java.util.regex.Pattern;
public class Main {
public static void main(String args[]) {
Pattern p = Pattern.compile("test");
StringBuffer sb = new StringBuffer();
String candidateString = "This is a test.";
String replacement = "Test";
Matcher matcher = p.matcher(candidateString);
matcher.find();
matcher.appendReplacement(sb, replacement);
}
}