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04-課後作業1-字符串加密

static 錯誤 logs con left util ann ont 設計思想

1.程序設計思想:

程序首先需要獲取要加密的或者待解密字符串,然後通過算法進行字符錯位,關鍵也是字符的錯位,最後直接調用函數輸出字符串。

2.程序流程圖:

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3.源程序:

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

        System.out.print("請選擇操作(1.加密、2.解密):");  
        Scanner sc = new Scanner(System.in);   
        int index = sc.nextInt();  
  
        if (1 == index) {  
            System.out.print("請輸入字符串:");  
            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("加密後的字符串是:" + newStr.toString());  
        } else if (2 == index) { 
            System.out.print("請輸入字符串:");  
            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("解密後的字符串是:");  
            for (int i = 0; i < arr.length; i++) {  
                System.out.print(arr[i]);  
            }  
        } else {  
            System.out.println("輸入錯誤,請輸入1或2");  
        }  
        sc.close();  
    }  
}  

4.程序結果截圖;

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04-課後作業1-字符串加密