Java- 移动 ROT13 字符串

Question

我想将 ROT13 字符串移动用户输入的量。这是示例输出：

Enter your text to encrypt (!!! to quit): abcdefghijklmnopqrstuvwxyz

Enter amount to shift text by: 3

ORIGINAL: abcdefghijklmnopqrstuvwxyz

ENCRYPTED: defghijklmnopqrstuvwxyzabc

用户必须提供 0 到 26 之间的偏移值。如果用户超出此范围，程序应强制用户输入有效值：

Enter your text to encrypt (!!! to quit): the quick brown fox jumped over the lazy dog
Enter amount to shift text by: -3
ERROR! Shift must be non-negative!
Enter amount to shift text by: 33
ERROR! Shift must be no more than 26!
Enter amount to shift text by: 2

输入要加密的文本（!!! 退出）：!!! 再见！

这是我编写的代码：

import java.util.Scanner;

public class Lab08b 
{

public static void main(String[] args)
{
    Scanner sc = new Scanner (System.in);
    String input = getText(sc);
    int shift = getShift(sc);
    if (input.equals("!!!"))
    {
        System.out.println("Goodbye!");
    }

    while (!input.equals("!!!"))
    {
        String encoded = rot13(input);
        shiftMessage(input, shift);
        displayResults(input, encoded);
        input = getText(sc);
        if (input.equals("!!!"))
        {
            System.out.println("Goodbye!");
        }
    }


}
private static int getShift (Scanner inScanner)
{
    System.out.print("Enter amount to shift text by: ");
    int shift = inScanner.nextInt();

    if (shift < 0)
    {
        System.out.println("ERROR! Shift must be non-negative!");
        System.out.print("Enter amount to shift text by: ");
        shift = inScanner.nextInt();
    }
    else if (shift > 26)
    {
        System.out.println("ERROR! Shift must be non-negative!");
        System.out.print("Enter amount to shift text by: ");
        shift = inScanner.nextInt();
    }
    return shift;
}

private static String getText(Scanner inScanner)
{
    System.out.print("Enter your text to encrypt (!!! to quit): ");
    String original = inScanner.nextLine();

    while (original.equals(""))
    {
        System.out.println("ERROR! String must not be empty!");
        System.out.print("Enter your text to encrypt (!!! to quit): ");
        original = inScanner.nextLine();
    }
    return original;
}


private static String rot13(String input)
{
    String str = "";

    for (int i = 0; i < input.length(); i++)
    {
        char ch = input.charAt(i);
        if (ch >= 'A' && ch <= 'Z')
        {
            ch = (char) (ch + 13);
            if (ch > 'Z')
            {
                ch = (char)(ch - 26);
            }
        }
        else if (ch >= 'a' && ch <= 'z')
        {
            ch = (char)(ch + 13);
            if (ch > 'z')
            {
                ch = (char)(ch - 26);
            }
        }
        str = str + ch;
    }
    return str;
}

private static void displayResults(String inText, String encText)
{
    System.out.print("+");
    for (int i = 13 + encText.length(); i > 0; i--)
    {
        System.out.print("-");
    }
    System.out.println("+");

    System.out.println("| ORIGINAL:  " + inText + " |");
    System.out.println("| ENCRYPTED: " + encText + " |");

    System.out.print("+");
    for(int i = 13 + encText.length(); i > 0; i--){
        System.out.print("-");
    }
    System.out.println("+");
}

private static String shiftMessage(String input, int n)
{
    for (int i = 0; i < input.length(); i++)
    {
        input = input.charAt(input.length()- n) + input.substring(0,input.length());
    }
    return input;
}

}

更新：这段代码是我取得进展的方式。实际换挡还是不行 http://pastebin.com/v2T1fxEj

我有它打印出 ROT13 加密和所有内容，我只是不知道如何转换它。

此外，当我尝试在 String input = getText(sc) 下面的主要方法中添加 "Enter amount to shift by" 时，我最终得到了这个：

Enter your text to encrypt (!!! to quit): ERROR! String must not be empty!
Enter your text to encrypt (!!! to quit):

我不应该得到那个

Answer 1

shiftMessage() 就像 rot13()，只是输入 n 而不是 13:

private static String shiftMessage(String input, int n) {
    String str = "";

    for (int i = 0; i < input.length(); i++)
    {
        char ch = input.charAt(i);
        if (ch >= 'A' && ch <= 'Z')
        {
            ch = (char) (ch + n);
            if (ch > 'Z')
            {
                ch = (char)(ch - 26);
            }
        }
        else if (ch >= 'a' && ch <= 'z')
        {
            ch = (char)(ch + n);
            if (ch > 'z')
            {
                ch = (char)(ch - 26);
            }
        }
        str = str + ch;
    }
    return str;
}

现在，当我从 main() 调用 shiftMessage() 而不是 rot13() 时，我可以：

Enter your text to encrypt (!!! to quit): abcdefghijklmnopqrstuvwxyz
Enter amount to shift text by: 1
+---------------------------------------+
| ORIGINAL:  abcdefghijklmnopqrstuvwxyz |
| ENCRYPTED: bcdefghijklmnopqrstuvwxyza |
+---------------------------------------+

其他问题：

你说的

ERROR! String must not be empty!是Scanner.nextInt()的经典。 nextInt() 只读取数字，不读取后面的换行符。因此，当您随后执行 inScanner.nextLine() 时，它会读取换行符和 returns 空字符串。我相信解决方案是在 nextInt() 之后调用 nextLine() 以摆脱换行符。

最后，您无法提前知道用户只会输入一次错误的班次金额。我能做到：

Enter your text to encrypt (!!! to quit): abc
Enter amount to shift text by: -3
ERROR! Shift must be non-negative!
Enter amount to shift text by: -3
+----------------+
| ORIGINAL:  abc |
| ENCRYPTED: ^_` |
+----------------+

Java- 移动 ROT13 字符串

Java- shifting a ROT13 string

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rot13