static Map<Character, Integer> smallcharintmap = new HashMap<>();
static Map<Integer, Character> smallintcharmap = new HashMap<>();

static Map<Character, Integer> capscharintmap = new HashMap<>();
static Map<Integer, Character> capsintcharmap = new HashMap<>();

static {
    char smallstart = 'a';
    char capstart = 'A';

    for(int i=1;i<=26;i++) {
        smallcharintmap.put(smallstart, i);
        smallintcharmap.put(i, smallstart);
        smallstart++;

        capscharintmap.put(capstart, i);
        capsintcharmap.put(i, capstart);
        capstart++;
    }
}

public static String caesarCipher(String str, int k) {
    StringBuilder resultBuilder = new StringBuilder();
    for(int i = 0; i < str.length(); i++) {
        Character ch = str.charAt(i);
        if(Character.isAlphabetic(ch)) {
            if(Character.isLowerCase(ch)) {
                int key = (smallcharintmap.get(ch) + k)%26;
                resultBuilder.append(smallintcharmap.get(key == 0 ? 26 : key));
            } else if(Character.isUpperCase(ch)) {
                int key = (capscharintmap.get(ch) + k)%26;
                resultBuilder.append(capsintcharmap.get(key == 0? 26 : key));
            }
        } else {
            resultBuilder.append(ch);
        }
    }
    return resultBuilder.toString();
}