Program to Encrypt Text Depending on the Length of a Word

Question

I wanted to make a program to encrypt text depending on its length. For example if the word was "test", then because "test" has 4 letters, it will shift each letter in the word to the 4th next letter. This would make "test" to "xiwx". I have made part of my program already. Here is it:

public static void main(String[] args){
    string.toLowerCase();
    int charPos = 0;
    int length = 0;

    for(int i = 0; i < string.length(); i++){
        charPos = 0;
        length = 0;
        while(!(string.charAt(i) == ' ')){
            length = charPos;
            charPos++;
        }
        length--;
        for(int j = 0; j<=length; j++){
            char cha =string.charAt(i);

            //HERE IS WHERE THE CHAR ADDING WILL HAPPEN

        }
        i++;

    }

}//end

Answer 1

There is a simpler way to achieve this type of encryption just by using one loop.

Encryption:

String str = "test"; // normal string

String encryptedStr = ""; // start empty then add characters

for (char ch : str.toCharArray()) // loop through each character in str

    encryptedStr += (char) (ch + str.length()); // need to cast addition to char

System.out.println("Encrypted String: " + encryptedStr); // output encrypted string

So the idea is to use the length() method to get the length of the string, as that's what you're adding to each character. Because each character has an ASCII integer value, we can perform math operations on them (so in this case, adding the length to each character). Then, since the result will be an integer, we must add a (char) cast to the result to convert it back to a character. Then we can concatenate this character to the empty string. If we do this with each character in the original string (by using a for loop and converting the string to a char array), we'll eventually get the encrypted string at the end.

The same idea works with Decryption:

String str = "xiwx"; // encrypted string

String decryptedStr = ""; // start empty then add characters

for (char ch : str.toCharArray()) // loop through each character in str

    decryptedStr += (char) (ch - str.length()); // need to cast subtraction to char

System.out.println("Decrypted String: " + decryptedStr); // output decrypted string

Except we subtract the length from each character.

Hope this helped :)