JAVA編寫一個加密及解密程式

加密解密程式

思想加密，先得到明文和密鑰，判斷明文的每個字元是小寫字母還是大寫字母，在根據密鑰進行取模移位。解密的思想跟加密類似。

加密：

package com.company;
import java.util.Scanner;
public class Encrypt {
    public static void Encrypt() {
        System.out.println("請輸入明文：");
        Scanner scanner1 = new Scanner(System.in);
        String str1 = scanner1.nextLine();
        System.out.println("請輸入密鑰:");
        Scanner scanner = new Scanner(System.in);
        int key1 = scanner.nextInt();
        String string="";
		for(int i=0;i<str1.length();i++) {
        char c=str1.charAt(i);
        if(c>='a'&&c<='z')
        {
            c+=key1%26;
            if(c<'a') c+=26;

            if(c>'z') c-=26;
        }else if(c>='A'&&c<='Z')
        {
            c+=key1%26;
            if(c<'A') c+=26;
            if(c>'Z') c-=26;
        }
        string =string+c;
    }
		System.out.println("加密後為："+string);
}
}

           

解密：

package com.company;
import java.util.Scanner;
public class Decrypt {
    public  void Decrypt() {
        System.out.println("請輸入密文:");
        Scanner scanner1 = new Scanner(System.in);
        Scanner scanner = new Scanner(System.in);
        String str2 = scanner1.nextLine();
        System.out.println("請輸入密鑰：");
        int key2 = scanner.nextInt();
        key2 = -key2;
        String string="";
        for(int i=0;i<str2.length();i++) {
            char c=str2.charAt(i);
            if(c>='a'&&c<='z')
            {
                c+=key2%26;
                if(c<'a') c+=26;
                if(c>'z') c-=26;
            }else if(c>='A'&&c<='Z')
            {
                c+=key2%26;
                if(c<'A') c+=26;
                if(c>'Z') c-=26;
            }
            string =string+c;
        }
        System.out.println("解密後為："+string);
    }
}

           

實作：

package com.company;
import java.util.Scanner;
public class Application {
    public static void main(String[] args) {
        int c;
        do {
            System.out.println("選擇功能：1:加密功能  2:解密功能 3:退出");
            Scanner scanner = new Scanner(System.in);
             c = scanner.nextInt();
            switch (c) {
                case 1: {
                    Encrypt encrypt = new Encrypt();
                    encrypt.Encrypt();
                    break;
                }
                case 2: {
                    Decrypt decrypt = new Decrypt();
                    decrypt.Decrypt();
                }
            }
        }
        while (c !=3);
        if(c == 3) System.out.println("歡迎再次使用");
    }
}
           

運作結果：