Question

我正在尝试创建一个Caesar Shift密码加密和解密程序。我需要它能够接受用户输入，直到用户希望退出（q），但我最终只是重复一切。

这是我的班级

import java.util.Scanner;
public class CaesarShift
{
//initialize private string for the alphabet
private final String ALPHABET = "abcdefghijklmnopqrstuvwxyz";
//public encryption code
public String encryptionMethod(String normText, int caesarShift)
{
    normText = normText.toLowerCase();
    String cipherText = "";
    for (int a = 0; a < normText.length(); a++)
    {
        int charP = ALPHABET.indexOf(normText.charAt(a));
        int shiftValue = (caesarShift + charP) % 26;
        char replaceValue = this.ALPHABET.charAt(shiftValue);
        cipherText += replaceValue;
    }
    return cipherText;
}
public String decryptionMethod(String cipherText,int caesarShift)
{
    cipherText = cipherText.toLowerCase();
    String normText = "";
    for (int a = 0; a < cipherText.length(); a++)
    {
        int charP = this.ALPHABET.indexOf(cipherText.charAt(a));
        int keyValue = (charP - caesarShift) % 26;
        if(keyValue < 0)
        {
            keyValue = this.ALPHABET.length() + keyValue;
       }
       char replaceValue = this.ALPHABET.charAt(keyValue);
       normText += replaceValue;
    }
    return normText;
}

}

这是我的测试器方法，我尝试实例化while循环

import java.util.Scanner;
public class CaesarShiftTester
{
public static void main(String args[])
{
    //import of the scanner method to ask the user for the input they would like
    Scanner in = new Scanner(System.in);
    System.out.println("What is the text you would like to do something with?(q to quit)");
    String normText = in.nextLine();
    System.out.println("What is the Caesar Shift Value?");
    int caesarShift = in.nextInt();
    //new declaration of the CaesarShift class to report back to easily
    CaesarShift shift = new CaesarShift();
    //declare the while method loop
    while(normText != "q")
    {
    //decalre the need properties for the encryption
    String cipherText = shift.encryptionMethod(normText, caesarShift);
    System.out.println("Your normal text is: " + normText);
    System.out.println("Your text after encryption is: " + cipherText);
    String cnormText = shift.decryptionMethod(cipherText, caesarShift);
    System.out.println("Your encrypted text is: " + cipherText);
    System.out.println("Your decrypte text is: " + cnormText);
}
}

}

Answer 1

while(normText != "q")

这是你的问题。 ==和!=运算符用于比较引用，而不是值。

将其更改为：

while(!q.equals(normText))

Answer 2

您永远不会在while循环内提示任何用户输入，因此它永远在旋转。在循环中添加用户输入检查：

while (!normText.equals("q")) {
    String cipherText = shift.encryptionMethod(normText, caesarShift);
    System.out.println("Your normal text is: " + normText);
    System.out.println("Your text after encryption is: " + cipherText);
    String cnormText = shift.decryptionMethod(cipherText, caesarShift);
    System.out.println("Your encrypted text is: " + cipherText);
    System.out.println("Your decrypte text is: " + cnormText);

    System.out.println("What is the text you would like to do something with?(q to quit)");
    normText = in.nextLine();
}

正如@Stultuske在他的回答中提到的那样，你也试图在使用String内部使用!=运算符比较String.equals()的值。但是不检查while循环内的用户输入是一个更大的问题。

虽然循环导致重复一遍又一遍，java

2 个答案: