04-课后作业1-字符串加密

Posted 2020-10-12 江槐

1.程序设计思想：

程序首先需要获取要加密的或者待解密字符串，然后通过算法进行字符错位，关键也是字符的错位，最后直接调用函数输出字符串。

2.程序流程图：

3.源程序：

import java.util.Scanner;  
  
public class Caesarcipher {  
    public static void main(String[] args) {  

        System.out.print("请选择操作（1.加密、2.解密）：");  
        Scanner sc = new Scanner(System.in);   
        int index = sc.nextInt();  
  
        if (1 == index) {  
            System.out.print("请输入字符串：");  
            String str = sc.next();  
  
            StringBuffer newStr = new StringBuffer();
            for (int i = 0; i < str.length(); i++) 
            {  
                char c = str.charAt(i);  
                switch (c) 
                {  
                case \'x\':  
                    newStr.append(\'a\');  
                    break;  
                case \'y\':  
                    newStr.append(\'b\');  
                    break;  
                case \'z\':  
                    newStr.append(\'c\');  
                    break;  
                default:  
                    if (!(c >= \'a\' && c <= \'w\')) {
                        newStr.append(c);  
                        continue;  
                    }  
                    char newChar = (char) (c + 3);
                    newStr.append(newChar);  
                }  
            }  
            System.out.println("加密后的字符串是：" + newStr.toString());  
        } else if (2 == index) { 
            System.out.print("请输入字符串：");  
            String str = sc.next();  
  
            char[] arr = str.toCharArray();
            for (int i = 0; i < arr.length; i++) {  
                switch (arr[i]) {  
                case \'a\':  
                    arr[i] = \'x\';  
                    break;  
                case \'b\':  
                    arr[i] = \'y\';  
                    break;  
                case \'c\':  
                    arr[i] = \'z\';  
                    break;  
                default:  
                    if (!(arr[i] >= \'d\' && arr[i] <= \'z\')) {
                        continue;  
                    }  
                    arr[i] -= 3;  
                }  
            }  
            System.out.print("解密后的字符串是：");  
            for (int i = 0; i < arr.length; i++) {  
                System.out.print(arr[i]);  
            }  
        } else {  
            System.out.println("输入错误,请输入1或2");  
        }  
        sc.close();  
    }  
}  

4.程序结果截图;