Question

我只是一名初学程序员，我在这里找到我程序中的错误。该程序只读取我的文本文件中的大写字母，即使我的加密和解密方法中有一个小写的情况。我猜测它是caesarEncipher方法的一个问题。（忽略我在主要方面的解读案例，我很快就会谈到它。）

import java.util.*;
import java.io.*;

public class Cipher {

    public static void main(String[] args) throws FileNotFoundException {
        Scanner scan = new Scanner(System.in);
        System.out.println("Welcome to CaesarCipher");
        System.out.println();
        System.out.println("Enter 1 to Encipher, 2 to Decipher, or -1 to exit");
        int choice = 0;
        do {
            choice = scan.nextInt();
            if (choice == 1) {
                System.out.println("What non-negative shift should be used?");
                int shift = scan.nextInt();
                System.out.println("What is the input file name?");
                String input = scan.next();
                System.out.println("What is the output file name?");
                String output = scan.next();
                System.out.println(caesarEncipher(input, shift, output));
            } else if (choice == 2) {

            } else if (choice == -1) {
                System.out.println("Thank you for using CaesarCipher");
                break;
            }
        } while (choice != 1 && choice != 2 && choice != -1);
    }

    public static String caesarEncipher(String inputString, int shift, String output) throws FileNotFoundException {
        File outFile = new File(output);
        PrintStream encoded = new PrintStream(outFile);  // creates new file for the output
        File input = new File(inputString);  // creates file with String to scan
        Scanner scan = new Scanner(input); // creates Scanner
        while (scan.hasNextLine()) {
            String cipher = scan.nextLine();            // gets next line of file
            String encipher = "";                   // String to be added to new file
            int i;
            for (i = 0; i < cipher.length(); i++) {
                String curr = cipher.substring(i, i + 1);  // current character
                String newChar = encrypt(curr, shift);
                encipher = encipher + newChar;
            }
            encoded.println(encipher);
        }
        encoded.close();
        return "DONE";
    }

    public static String encrypt(String str, int shift) {
        String encrypted = "";
        for (int i = 0; i < 1; i++) {
            int c = str.charAt(i);
            if (Character.isUpperCase(c)) {//if uppercase
                c = c + (shift % 26);
                if (c > 'Z') { //resets if it passes 'Z'
                    c = c - 26;
                } else if (Character.isLowerCase(c)) {// if lowercase
                    c = c + (shift % 26);
                    if (c > 'z') { // resets if it passes 'z'
                        c = c - 26;
                    }
                }
                encrypted = encrypted + (char) c; // adds the encrypted character to the string
            }
        }
        return encrypted;
    }

    public static String decrypt(String str, int shift) {
        String decrypted = "";
        for (int i = 0; i < 1; i++) {
            int c = str.charAt(i);
            if (Character.isUpperCase(c)) //if uppercase
            {
                c = c + (shift % 26);
                if (c < 'A') { //resets if it passes 'A'
                    c = c + 26;
                }
            } else if (Character.isLowerCase(c)) // if lowercase
            {
                c = c + (shift % 26);
                if (c < 'a') { // resets if it passes 'a'
                    c = c + 26;
                }
            }
            decrypted = decrypted + (char) c; // adds the derypted character to the string
        }
        return decrypted;
    }
}

Answer 1

在encrypt()方法中：代码的这一部分

else if(Character.isLowerCase(c)) {
        c=c+(shift%26);
        if(c>'z') { 
            c=c-26;
        }
    }
    encrypted=encrypted+(char)c;

属于if(c>'Z')而不是if(Character.isUpperCase(c))

使用Java代码的Caesar Cipher - 只会读取大写

1 个答案: