предложение с большой буквы

package tasks3;

import com.sun.deploy.util.StringUtils;
import com.sun.xml.internal.fastinfoset.util.PrefixArray;

import java.util.Arrays;
import java.util.Scanner;
import java.util.StringJoiner;


public class Hello1 {
    public static String join() {
        Scanner scanner = new Scanner(System.in);
        System.out.println("Input sentence: ");
        String a = scanner.nextLine();
        String delimiter = "\\.";
        String[] sentences = a.split(delimiter);
        for (int i = 0; i < sentences.length; i++) {
            String sentence = ltrim(sentences[i]);
            String head = sentence.substring(0, 1).toUpperCase();
            String tail = sentence.substring(1);
            String newString = head + tail;
            sentences[i] = newString;
        }
        String join = String.join(delimiter, sentences);
        return join;
    }

    public static String ltrim(String s) {
        int i = 0;
        while (i < s.length() && Character.isWhitespace(s.charAt(i))) {
            i++;
        }
        return s.substring(i);
    }

    public static void main(String[] args) {
        System.out.println(join());
    }
}