Caesar Cipher with key in java

Question

我正在用java编写这个ceasar密码加密程序。在这里，您要求用户输入文本和用于加密文本的密钥。如果他们不输入数字，它将输入一个随机数字。还没试着解密文本。在第29行也得到一个错误，cmd一直在说二元运算符的操作数类型不正确。

            import java.util.Scanner;
            import java.util.Random;
            public class A {
                public static void main(String[] args) {
                    System.out.println("This program encrypts text you enter using the Caesar Cipher.\n");
                    Scanner sc = new Scanner(System.in);
                    String text;
                    String line;
                    String choice;
                    String shift;
                    char[] alphabet = {'A', 'B','C','D','E', 'F','G','H','I','J','K','L','M','N','O','P','Q','R','S','T','U','V','W','X','Y','Z'};
                    int key;
                    int caeserVal;
                    int sum;
                    String doAgain;

                    do {
                        System.out.println("Enter a line text to encrypt: ");
                        line = sc.nextLine();
                        System.out.print("Enter the key between -25 and 25. Enter 0 to have it generate a random key: ");
                        key = sc.nextInt();
                        sum = 0;
                        char[] plaintext = args[0].toCharArray();
                        shift = args[1];

                        for(int i = 0; i < plaintext.length; i++) {
                            for(int j = 0; j < alphabet.length; j++) {
                                if(alphabet[j] == plaintext[i]) {
                                    plaintext[i] = alphabet[(j + shift) % alphabet.length];
                            }
                        }
                    }
                            String ciphertext = new String(plaintext);
                            System.out.println(ciphertext);
                            caeserVal = sum + key;
                        System.out.printf("The text encrypted with key %d is %s.\n", key,caeserVal);
                        System.out.print("Try again(y or n)? ");
                        choice = sc.nextLine().toUpperCase();
                    }while(choice.equals("Y"));
                    System.out.println("Thank you for using this program.");



                }
            }

Answer 1

如果第二个命令行参数是整数

 import java.util.Scanner;
            import java.util.Random;
            public class A {
                public static void main(String[] args) {
                    System.out.println("This program encrypts text you enter using the Caesar Cipher.\n");
                    Scanner sc = new Scanner(System.in);
                    String text;
                    String line;
                    String choice;
                    String shift;
                    char[] alphabet = {'A', 'B','C','D','E', 'F','G','H','I','J','K','L','M','N','O','P','Q','R','S','T','U','V','W','X','Y','Z'};
                    int key;
                    int caeserVal;
                    int sum;
                    String doAgain;

                    do {
                        System.out.println("Enter a line text to encrypt: ");
                        line = sc.nextLine();
                        System.out.print("Enter the key between -25 and 25. Enter 0 to have it generate a random key: ");
                        key = sc.nextInt();
                        sum = 0;
                        char[] plaintext = args[0].toCharArray();
                        shift = args[1];

                        for(int i = 0; i < plaintext.length; i++) {
                            for(int j = 0; j < alphabet.length; j++) {
                                if(alphabet[j] == plaintext[i]) {
                                    plaintext[i] = alphabet[((j + Integer.parseInt(shift)) % alphabet.length)];
                            }
                        }
                    }
                            String ciphertext = new String(plaintext);
                            System.out.println(ciphertext);
                            caeserVal = sum + key;
                        System.out.printf("The text encrypted with key %d is %s.\n", key,caeserVal);
                        System.out.print("Try again(y or n)? ");
                        choice = sc.nextLine().toUpperCase();
                    }while(choice.equals("Y"));
                    System.out.println("Thank you for using this program.");



                }
            }

如果它不是整数，那么它将抛出一个错误。