Сделать код элегантным

public class Program {
    public static String Puzzle(String s) {
        char[] chars = s.toCharArray();
        for (int i = 0; i < chars.length; i++)
        {
            if (i==chars.length-1 || chars[i+1]==' ')
                chars[i]=Character.toUpperCase(chars[i]);
        }
        return new String(chars);
    }
}

Как-то так:

private static String lastToUpperCase(String text) {
    String res = "";
    for (String s : text.split("\\b"))
        res += s.substring(0, s.length() - 1)
                + s.substring(s.length() - 1).toUpperCase();
    return res;
}

Input: I want to walk my dog. Печатает: I wanT tO walK mY doG.

используя

import org.apache.commons.lang3.StringUtils;
import org.apache.commons.lang3.text.WordUtils;

получается:

String inputString = "this string is needed to be last letter-uppercased for each word";
String outputString = StringUtils.reverse(WordUtils.capitalize(StringUtils.reverse(inputString)));
// System.out.println(outputString):
// thiS strinG iS needeD tO bE lasT letter-uppercaseD foR eacH worD

подглядел: https://stackoverflow.com/a/42302143/6104996

Например, так:

char[] с = (s + " ").toCharArray();
for (int i = 1; i < с.length; i++)
    if (с[i]==' ') 
        с[i-1]=Character.toUpperCase(с[i-1]);
return new String(с);