Made a Algorithm for cryptography using principles of Caedar Cipher, where we want to encrypt a message then for that we make a key and for every letter in the message we increase it's alphabet with +key letter e.g for "a" and key is 10 then the encrypt word will be "k".

CaesarCipher.java

package DataStructures;

public class CaesarCipher {
    static String encrypt(String msg, int key){
        StringBuilder encrypted = new StringBuilder(msg);
        String alphabets = "ABCDEFGHIJKLMNOPQRSTVUWXYZ";
        String smallalphabets = alphabets.toLowerCase();
        String shiftedAplhabets = alphabets.substring(key) + alphabets.substring(0, key);
        for( int i =0; i< encrypted.length(); i++){
            char curChar = encrypted.charAt(i);
            int idx = alphabets.indexOf(curChar);
            if(idx==-1){
                idx =  smallalphabets.indexOf(curChar);
            }
            if(idx !=-1){
                char newChar;
                if(isUppercased(String.valueOf(curChar))){
                    newChar = shiftedAplhabets.charAt(idx);
                }else {
                    newChar = shiftedAplhabets.toLowerCase().charAt(idx);
                }
                encrypted.setCharAt(i, newChar);
            }
        }
        return  encrypted.toString();
    }
    static boolean isUppercased(String str){
        return str == str.toUpperCase();
    }
    public static void main(String[] args) {
        String msg = "There is a cake on the table";
        System.out.println(encrypt(msg,12));
    }
}