凯撒密码后不读文字的空间，无法弄清楚为什么

Question

I need to write a simple Caesar cipher for an assignment and I have to encrypt the message "This is a Caesar cipher" with a left shift of 3. I have tried using an IF statement followed by 'continue;' but it is not working, I cannot for the life of me figure out what is causing this problem haha.

public static String encrypt(String plainText, int shiftKey) {
    plainText = plainText.toLowerCase();
    String cipherText = "";
    for (int i = 0; i < plainText.length(); i++) {
    char replaceVal = plainText.charAt(i);
    int charPosition = ALPHABET.indexOf(replaceVal);        
    if(charPosition != -1) {
        int keyVal = (shiftKey + charPosition) % 26;
        replaceVal = ALPHABET.charAt(keyVal);
    }

    cipherText += replaceVal;
    }
    return cipherText;
}
public static void main (String[] args) {
    String message;
    try (Scanner sc = new Scanner(System.in)) {
        System.out.println("Enter a sentence to be encrypted");
        message = new String();
        message = sc.next();
    }
 System.out.println("The encrypted message is");
 System.out.println(encrypt(message, 23));
}

}

Answer 1

You are only reading one word with Scanner.next() and never use new String() . Change

message = new String();
message = sc.next();

to

message = sc.nextLine();

It's also worth noting that StringBuilder and simple arithmetic is all you need for a Caesar Cipher. For example,

public static String encrypt(String plainText, int shiftKey) {
    StringBuilder sb = new StringBuilder(plainText);
    for (int i = 0; i < sb.length(); i++) {
        char ch = sb.charAt(i);
        if (!Character.isWhitespace(ch)) {
            sb.setCharAt(i, (char) (ch + shiftKey));
        }
    }
    return sb.toString();
}

public static void main(String[] args) {
    int key = 10;
    String enc = encrypt("Secret Messages Are Fun!", key);
    System.out.println(enc);
    System.out.println(encrypt(enc, -key));
}

Which outputs

]om|o~ Wo}}kqo} K|o Px+
Secret Messages Are Fun!