import java.util.*;
import java.io.*;

public class FirstLetter{
public static String capitalizeFirstLetter( String str ) {
final StringTokenizer st = new StringTokenizer( str, " ", true );
final StringBuilder sb = new StringBuilder();

while ( st.hasMoreTokens() ) {
String token = st.nextToken();
Character ch=Character.valueOf(token.charAt(0));
token = String.format( "%s%s",Character.toUpperCase(token.charAt(0)),token.substring(1) );
sb.append( token );
}
return sb.toString();
}
public static void main(String[]args) throws Exception{
System.out.print("Enter the sentence : ");
BufferedReader br =new BufferedReader(new InputStreamReader(System.in));
String inputString = br.readLine();
FirstLetter letter=new FirstLetter();
String words=letter.capitalizeFirstLetter(inputString);
System.out.println(words);
}
}

Why String class is final? what the motivation behind to make it final?