Question

对于在线Java课程，我正在编写Caesar Cipher。在这里，您输入一个字符串和一个移位编号，答案随移位字符串一起返回，其中所有字符都按移位编号将字母“向下”移位。对于我的程序，我还进行了分组练习，在该练习中，我必须将移位后的字符串分组为一定数量的组（例如，“ SGHSJDGDKGHSA”按3分组是“ SGH SJD GDK GHSA”）。如果字符串中的字符数不能被分组号整除，则程序会在字符串的末尾添加小写字母x（例如：“ SGHSJDGDKGHSA”，按4分组为“ SGHS JDGD KGHS Axxx”）。

我的程序一直工作到分组功能（我的代码中的groupify方法）。不返回带有组的字符串。有关如何解决此问题的任何建议？

import java.util.Scanner;

public class Crypto {

    public static void main (String[] args) {

        Scanner input = new Scanner(System.in);
        System.out.println("Enter a phrase.");
        String userText = input.nextLine();
        String normText = normalizeText(userText);

        System.out.println("Enter a shift.");
        String strUserShift = input.nextLine();
        int userShift = Integer.parseInt(strUserShift);
        String shiftText = shiftAlphabet(userShift, normText);
        System.out.println("Shifted Text: " + shiftText);

        System.out.println("Enter a grouping number.");
        String strUserGroupNum = input.nextLine();
        int userGroupNum = Integer.parseInt(strUserGroupNum);
        String encryptedText = groupify(shiftText, userGroupNum);
        System.out.print(encryptedText);

    }

    private static String normalizeText(String preText) {
        StringBuilder newText = new StringBuilder();
        for(int charNum = 0; charNum < preText.length(); charNum++) {
            char charText = preText.charAt(charNum);
            if (charText == '.' || charText == ',' || charText == ':' || charText == ';' || charText == '\'' || charText == '\\' || charText == '"' || charText == '!' || charText == '?' || charText == '(' || charText == ')') {
                newText.append("");
            } else {
                String stringText = "" + charText;
                stringText = stringText.toUpperCase();
                newText.append(stringText);
            }
        }
        return(newText.toString());
    }

    private static String shiftAlphabet(int shift, String normText) {
        StringBuilder shiftedText = new StringBuilder();
        String alphabet = "abcdefghijklmnopqrstuvwxyz".toUpperCase();
        for (int index = 0; index < normText.length(); index++) {
            char currentChar = normText.charAt(index);
            int currentCharNum = alphabet.indexOf(currentChar);

            int newCharNum = currentCharNum + shift;

            while (newCharNum >= 26 || newCharNum < 0) {
                if (newCharNum >= 26) {
                    newCharNum -= 26;
                } else {
                    newCharNum += 26;
                }
            }

            char newChar = alphabet.charAt(newCharNum);
            shiftedText.append(newChar);
        }
        return(shiftedText.toString());
    }

    private static String groupify(String shiftText, int groupNum) {
        StringBuilder sbShiftText = new StringBuilder();
        StringBuilder sbGroupText = new StringBuilder();
        String finalText = "";

        while (sbShiftText.length() % groupNum != 0) {
            sbShiftText.append("x");
        }

        for (int i = 1; i <= sbShiftText.length(); i++) {
            if (groupNum == 1) {
                finalText = shiftText;
            } else {
                // everything w group number > 1
                if (groupNum % i == 0) {
                    sbGroupText.append(" ");
                } else {
                    String tempStr = sbShiftText.charAt(i) + "";
                    sbGroupText.append(tempStr);
                }
                finalText = sbGroupText.toString();
            }
        }
        return(finalText);
    }
}

Answer 1

sbShiftText已定义但从未初始化，因此sbShiftText.length()无效。

应该是这样的： StringBuilder sbShiftText = new StringBuilder(shiftText);

Answer 2

下面是对工作https://repl.it/@omurbekjk/DesertedDistinctLight稍作修改的解决方案：

import java.util.Scanner;

public class Main {

    public static void main (String[] args) {

        Scanner input = new Scanner(System.in);
        System.out.println("Enter a phrase.");
        String userText = input.nextLine();
        String normText = normalizeText(userText);

        System.out.println("Enter a shift.");
        String strUserShift = input.nextLine();
        int userShift = Integer.parseInt(strUserShift);
        String shiftText = shiftAlphabet(userShift, normText);
        System.out.println("Shifted Text: " + shiftText);

        System.out.println("Enter a grouping number.");
        String strUserGroupNum = input.nextLine();
        int userGroupNum = Integer.parseInt(strUserGroupNum);
        String encryptedText = groupify(shiftText, userGroupNum);
        System.out.print(encryptedText);

    }

    private static String normalizeText(String preText) {
        StringBuilder newText = new StringBuilder();
        for(int charNum = 0; charNum < preText.length(); charNum++) {
            char charText = preText.charAt(charNum);
            if (charText == '.' || charText == ',' || charText == ':' || charText == ';' || charText == '\'' || charText == '\\' || charText == '"' || charText == '!' || charText == '?' || charText == '(' || charText == ')') {
                newText.append("");
            } else {
                String stringText = "" + charText;
                stringText = stringText.toUpperCase();
                newText.append(stringText);
            }
        }
        return(newText.toString());
    }

    private static String shiftAlphabet(int shift, String normText) {
        StringBuilder shiftedText = new StringBuilder();
        String alphabet = "abcdefghijklmnopqrstuvwxyz".toUpperCase();
        for (int index = 0; index < normText.length(); index++) {
            char currentChar = normText.charAt(index);
            int currentCharNum = alphabet.indexOf(currentChar);

            int newCharNum = currentCharNum + shift;

            while (newCharNum >= 26 || newCharNum < 0) {
                if (newCharNum >= 26) {
                    newCharNum -= 26;
                } else {
                    newCharNum += 26;
                }
            }

            char newChar = alphabet.charAt(newCharNum);
            shiftedText.append(newChar);
        }
        return(shiftedText.toString());
    }

    private static String groupify(String shiftText, int groupNum) {
        StringBuilder sbShiftText = new StringBuilder(shiftText);
        StringBuilder sbGroupText = new StringBuilder();
        String finalText = "";
        String temp = "";
        int remainder = sbShiftText.length() % groupNum; 
        while (remainder>0) {
            sbShiftText.append("x");
            remainder--;
        }
        int grouping = 0;
        System.out.println(sbShiftText);
        System.out.println(groupNum);
        for (int i = 0; i < sbShiftText.length(); i++) {
            temp += sbShiftText.charAt(i);
            grouping++;
            if (groupNum == grouping) {
                finalText += temp + " ";
                temp="";
                grouping=0;
            } 
        }
        return(finalText);
    }
}

Answer 3

首先尝试调试groupify（）方法。如果不知道如何调试它，那就学习它。

groupify（）方法中的问题是您声明此问题

StringBuilder sbShiftText = new StringBuilder();

sbShiftText为空，因此sbShiftText.length（）返回0。因此，while循环和for循环根本没有运行。

首先用shiftText之类初始化sbShiftText

StringBuilder sbShiftText = new StringBuilder(shiftText);

Answer 4

private static String groupify(String shiftText, int groupNum) {
        StringBuilder sbShiftText = new StringBuilder();
        StringBuilder sbGroupText = new StringBuilder();
        String finalText = "";

        *sbShiftText.append(shiftText);*
        while (sbShiftText.length() % groupNum != 0) {
            sbShiftText.append("x");
        }
        for (int i = 0; i <sbShiftText.length(); i++) {
            if (groupNum == 1) {
                finalText = shiftText;
            } 
            else {
                if (*i%groupNum* == 0&&i!=0) {
                    sbGroupText.append(" ");
                } 
                String tempStr = sbShiftText.charAt(i) + "";
                sbGroupText.append(tempStr);
                finalText = sbGroupText.toString();
            }
        }
        return finalText;
    }

程序未返回字符串

4 个答案: