开始学Java之18 简单字母加密解密程序

头秃了

头秃了唔…

第一版

（没有主哈哈）

加密：

（ShiftAlphabetEncrypt.java）

import java.util.Scanner;

public class ShiftAlphabetEncrypt{
  private static Scanner scan = new Scanner(System.in);
  private static String alph = "abcdefghijklmnopqrstuvwxyz";
  
  static String shiftAlphabet (int key){ 
      return alph.substring(key) + alph.substring(0,key);
  }
    
  public static String encrypt (String text, String alphShif, int key){
      StringBuilder t = new StringBuilder("");
      
      for (int i=0, n=text.length(); i<n; ++i){
          if (!(Character.isLetter(text.charAt(i)))) {
              t.append(text.charAt(i));
              continue;
          }
          
          for (int m=0, o=alph.length(); m<o; ++m){
            if ((Character.toLowerCase(text.charAt(i))) == alph.charAt(m)){
                if (Character.isUpperCase(text.charAt(i)))
                    t.append(Character.toUpperCase(alphShif.charAt(m)));
                else
                    t.append(alphShif.charAt(m));
            }
          }
      }
      return t.toString();
  }
  
  public static void main (String[] args){
      System.out.println("\n\n\nPlease enter the text that you want to encrypt:");
      String text = scan.nextLine();
      
      System.out.println("\nPlease enter the key (positive integer):");
      int key = scan.nextInt();
      scan.close();
        
      System.out.println(encrypt(text, shiftAlphabet(key), key));
    }
}

解密：

（ShiftAlphabetDecrypt.java）

import java.util.Scanner;

public class ShiftAlphabetDecrypt{
  private static Scanner scan = new Scanner(System.in);
  private static String alph = "abcdefghijklmnopqrstuvwxyz";
  
  static String shiftAlphabet (int key){ 
      return alph.substring(alph.length()-key) +
             alph.substring(0, alph.length()-key);
  }
  
  /*static String decrypt (String text, String alphShif, int key){
      StringBuilder t = new StringBuilder("");
      
      for (int i=0, n=text.length(); i<n; ++i){
          if (!(Character.isLetter(text.charAt(i)))) {
              t.append(text.charAt(i));
              continue;
          }
          
          for (int m=0, o=alph.length(); m<o; ++m){
            if ((Character.toLowerCase(text.charAt(i))) == alph.charAt(m)){
                if (Character.isUpperCase(text.charAt(i)))
                    t.append(Character.toUpperCase(alphShif.charAt(m)));
                else
                    t.append(alphShif.charAt(m));
            }
          }
      }
      return t.toString();
  }*/
  
  public static void main (String[] args){
      System.out.println("\n\n\nPlease enter the encrypted text:");
      String text = scan.nextLine();
      
      System.out.println("\nPlease enter the key (positive integer):");
      int key = scan.nextInt();
      
      //System.out.println(shiftAlphabet(key));
      //System.out.println(decrypt(text, shiftAlphabet(key), key));
      System.out.println(ShiftAlphabetEncrypt.encrypt(text, shiftAlphabet(key), key));
  }
}

输出：

加密：

Please enter the text that you want to encrypt:
I am alittlebear HAHA!!!

Please enter the key (positive integer):
13
V nz nyvggyrorne UNUN!!!

解密：

Please enter the encrypted text:
V nz nyvggyrorne UNUN!!!

Please enter the key (positive integer):
13
I am alittlebear HAHA!!!

解密需要加密文本和加密密钥…

第二版

加密：

//Import Scanner.
import java.util.Scanner;

public class ShiftAlphabetEncrypt{
  public static Scanner scan = new Scanner(System.in);
  public static String alph = "abcdefghijklmnopqrstuvwxyz";
  
  //Method that will shift the alphabet with keys what you entered in main method.
  static String[] shiftAlphabet (int[] key){ 
      String[] alphShif = {alph.substring(key[0])+alph.substring(0,key[0]), 
                           alph.substring(key[1])+alph.substring(0,key[1])};
      return alphShif;
  }
    
  //Method that encrypt/decrypt the text that you entered with keys in main method.
  public static String encrypt (String text, String[] alphShif, int[] key){
      StringBuilder t = new StringBuilder("");
      int count = 0;
      boolean oddEven = true;
      
      for (int i=0, n=text.length(); i<n; ++i){
        //If character not letter, nothing change.
        if (!(Character.isLetter(text.charAt(i)))) {
            t.append(text.charAt(i));
            continue;
        }
        
        ++count;
        
        //If character is not "not letter".
        for (int m=0, o=alph.length(); m<o; ++m){
          //See is this letter in odd or even position (count only letters).
          if (count%2==1) 
            oddEven=true; 
          else  
            oddEven=false;
          
          //Find the original position of this letter.
          if ((Character.toLowerCase(text.charAt(i))) == alph.charAt(m)){
              //If this letter is in upper case or not in upper case.
              if (Character.isUpperCase(text.charAt(i)))
                  //Change this letter to the number in same position of new alphabet.
                  t.append(Character.toUpperCase(alphShif[oddEven?0:1].charAt(m)));
              else
                  t.append(alphShif[oddEven?0:1].charAt(m));
          }
        }
      }
      //Return encrypted/decrypted text back.
      return t.toString();
  }
  
  //Main method.
  public static void main (String[] args){
      System.out.println("\n\n\nPlease enter the text that you want to encrypt:");
      String text = scan.nextLine();
      
      int[] key = new int[2];
      
      System.out.println("\nPlease enter the key of odd letters\n(positive integer):");
      key[0] = scan.nextInt();
      
      System.out.println("\nPlease enter the key of even letters\n(positive integer):");
      key[1] = scan.nextInt();
      scan.close();
        
      System.out.println(encrypt(text, shiftAlphabet(key), key));
    }
}

解密：

//Import Scanner.
import java.util.Scanner;

public class ShiftAlphabetDecrypt{
  private static Scanner scan = new Scanner(System.in);
  private static String alph = "abcdefghijklmnopqrstuvwxyz";
  
  //Method that will shift the encrypted alphabet back
  //with keys what you entered in main method.
  static String[] shiftAlphabet (int[] key){ 
      String[] alphShif = {alph.substring(alph.length()-key[0])+
                                alph.substring(0, alph.length()-key[0]), 
                           alph.substring(alph.length()-key[1])+
                                alph.substring(0, alph.length()-key[1])};
      return alphShif;
  }
  
  //Main method.
  public static void main (String[] args){
      System.out.println("\n\n\nPlease enter the encrypted text:");
      String text = scan.nextLine();
      
      int[] key = new int[2];
      
      System.out.println("\nPlease enter the key of odd letters\n(positive integer):");
      key[0] = scan.nextInt();
      
      System.out.println("\nPlease enter the key of even letters\n(positive integer):");
      key[1] = scan.nextInt();
      scan.close();
      
      System.out.println(ShiftAlphabetEncrypt.encrypt(text, shiftAlphabet(key), key));
  }
}

输出：

加密：

Please enter the text that you want to encrypt:
Je m’appelle alittlebear!!

Please enter the key of odd letters
(positive integer):
6

Please enter the key of even letters
(positive integer):
16
Pu s’qvfkbru gbojzbkrkqx!!

解密：

Please enter the encrypted text:
Pu s’qvfkbru gbojzbkrkqx!!

Please enter the key of odd letters
(positive integer):
6

Please enter the key of even letters
(positive integer):
16
Je m’appelle alittlebear!!

解密需要加密文本和两个奇偶数加密密钥…

一会尝试解密不需要密钥，加密文本直接就能转换，想慢慢尝试做一个base64加密差不多的东西…我的思路是加密时在某个地方放上加密密钥，解密直接就能提取这个密钥，这样你没有解密代码也很难猜出来haha，当然新研发的那个量子计算机除外😓（我也不知道我在说啥别理我自嗨hh）。。

第三版

加密：

//Import Scanner.
import java.util.Scanner;

public class ShiftAlphabetEncrypt {
  public final static Scanner scan = new Scanner(System.in);
  public final static String alphabet = "abcdefghijklmnopqrstuvwxyz";

  // Method that will shift the alphabet with keys what you entered in main method.
  static String[] shiftAlphabetEncrypt(int[] keys) {
    String[] alphaShifted = { 
      alphabet.substring(keys[0]) + alphabet.substring(0, keys[0]),
      alphabet.substring(keys[1]) + alphabet.substring(0, keys[1])};

    return alphaShifted;
  }

  // Method that encrypt/decrypt the text that you entered with keys in main method.
  public static String encryptAndDecrypt (String text, String[] alphaShifted, int[] keys) {
    StringBuilder textSB = new StringBuilder("");
    int count = 0;
    boolean oddEven = true;
    char textCA;

    for (int i = 0, a = text.length(); i < a; ++i) {
      textCA = text.charAt(i);

      // If character not letter, nothing change.
      if (!(Character.isLetter(textCA))) {
        textSB.append(textCA);
        continue;
      }

      ++count;
      // See is this letter in odd or even position (count only letters).
      if (count % 2 == 1)
        oddEven = true;
      else
        oddEven = false;

      // If this character is not "not letter" (is letter).
      for (int b = 0, c = alphabet.length(); b < c; ++b) {
        

        // Find the original position of this letter.
        if ((Character.toLowerCase(textCA)) == alphabet.charAt(b))

          // Change this letter to the number in same position of new alphabet.
          textSB.append(Character.isUpperCase(textCA) ?   //Ask is this letter in upper case?
                       (Character.toUpperCase(alphaShifted[oddEven ? 0 : 1].charAt(b))) : //Append an upper case letter.
                       (alphaShifted[oddEven ? 0 : 1].charAt(b)));  //Append a lower case letter (no change).
      }
    }

    // Return encrypted/decrypted text back.
    return textSB.toString();
  }

  // Main method.
  public static void main (String[] args){
    scan.reset();
    System.out.println("\n\n\nPlease enter the text that you want to encrypt:");
    String text = scan.nextLine();
    
    int[] keys = new int[2];
    
    System.out.println("\nPlease enter the keys of odd letters\n(positive integer):");
    keys[0] = scan.nextInt();
    
    System.out.println("\nPlease enter the keys of even letters\n(positive integer):");
    keys[1] = scan.nextInt();
    scan.close();
      
    System.out.println(encryptAndDecrypt(text, shiftAlphabetEncrypt(keys), keys));
  }
}

解密：

//Import Scanner.
import java.util.Scanner;
import ShiftAlphabetEncrypt;

public class ShiftAlphabetDecrypt{
  private final static Scanner scan = ShiftAlphabetEncrypt.scan;
  private final static String alph = ShiftAlphabetEncrypt.alphabet;
  
  //Method that will shift the encrypted alphabet back
  //with keys what you entered in main method.
  static String[] shiftAlphabetDecrypt (int[] keys){ 
      String[] alphabetShifted = {alph.substring(alph.length()-keys[0])+
                                  alph.substring(0, alph.length()-keys[0]),
                                  alph.substring(alph.length()-keys[1])+
                                  alph.substring(0, alph.length()-keys[1])};
      return alphabetShifted;
  }
  
  //Main method.
  public static void main (String[] args){
    scan.reset();
    System.out.println("\n\n\nPlease enter the encrypted text:");
    String text = scan.nextLine();
    
    int[] keys = new int[2];
    
    System.out.println("\nPlease enter the keys of odd letters\n(positive integer):");
    keys[0] = scan.nextInt();
     
    System.out.println("\nPlease enter the keys of even letters\n(positive integer):");
    keys[1] = scan.nextInt();
    scan.close();
     
    System.out.println(ShiftAlphabetEncrypt.encryptAndDecrypt(text, shiftAlphabetDecrypt(keys), keys));
  }
}

输出：

加密：

Please enter the text that you want to encrypt:
WO SHI ALITTLEBEAR LOL!!

Please enter the keys of odd letters
(positive integer):
3

Please enter the keys of even letters
(positive integer):
7
ZV VOL HOPWAOLELDY OVO!!

解密：

Please enter the encrypted text:
ZV VOL HOPWAOLELDY OVO!!

Please enter the keys of odd letters
(positive integer):
3

Please enter the keys of even letters
(positive integer):
7
WO SHI ALITTLEBEAR LOL!!

尽力改代码了…我改不动了😴。。。晚点研究上面那个问题

第四版

加密：

//Import Scanner.
import java.util.Scanner;

public class ShiftAlphabetEncrypt {
  public final static Scanner scan = new Scanner(System.in);
  public final static String alphabet = "abcdefghijklmnopqrstuvwxyz";


  static String encryptKeys(int[] key){
    StringBuilder keysLetters = new StringBuilder("");
    for (int n=0; n<2; ++n){
      keysLetters.append(alphabet.charAt(key[n]));
    }
    return keysLetters.toString();
  }

  // Method that will shift the alphabet with keys what you entered in main method.
  static String[] shiftAlphabetEncrypt(int[] keys) {
    String[] alphaShifted = { 
      alphabet.substring(keys[0]) + alphabet.substring(0, keys[0]),
      alphabet.substring(keys[1]) + alphabet.substring(0, keys[1])};

    return alphaShifted;
  }

  // Method that encrypt/decrypt the text that you entered with keys in main method.
  public static String encryptAndDecrypt (String text, String[] alphaShifted, int[] keys) {
    StringBuilder textSB = new StringBuilder("");
    int count = 0;
    boolean oddEven = true;
    char textCA;

    for (int i = 0, a = text.length(); i < a; ++i) {
      textCA = text.charAt(i);

      // If character not letter, nothing change.
      if (!(Character.isLetter(textCA))) {
        textSB.append(textCA);
        continue;
      }

      ++count;
      // See is this letter in odd or even position (count only letters).
      if (count % 2 == 1)
        oddEven = true;
      else
        oddEven = false;

      // If this character is not "not letter" (is letter).
      for (int b = 0, c = alphabet.length(); b < c; ++b) {
        

        // Find the original position of this letter.
        if ((Character.toLowerCase(textCA)) == alphabet.charAt(b))

          // Change this letter to the number in same position of new alphabet.
          textSB.append(Character.isUpperCase(textCA) ?   //Ask is this letter in upper case?
                       (Character.toUpperCase(alphaShifted[oddEven ? 0 : 1].charAt(b))) : //Append an upper case letter.
                       (alphaShifted[oddEven ? 0 : 1].charAt(b)));  //Append a lower case letter (no change).
      }
    }

    // Return encrypted/decrypted text back.
    return textSB.toString();
  }

  // Main method.
  public static void main (String[] args){
    scan.reset();
    System.out.println("\n\n\nPlease enter the text that you want to encrypt:");
    String text = scan.nextLine();
    
    int[] keys = new int[2];
    
    System.out.println("\nPlease enter the key of odd letters\n(positive integer):");
    keys[0] = scan.nextInt();
    
    System.out.println("\nPlease enter the key of even letters\n(positive integer):");
    keys[1] = scan.nextInt();
    scan.close();
      
    System.out.println(encryptKeys(keys)+encryptAndDecrypt(text, shiftAlphabetEncrypt(keys), keys));
  }
}

解密：

//Import Scanner.
import java.util.Scanner;
import ShiftAlphabetEncrypt;

public class ShiftAlphabetDecrypt{
  private final static Scanner scan = ShiftAlphabetEncrypt.scan;
  private final static String alphabet = ShiftAlphabetEncrypt.alphabet;
  public static String text;
  public static int[] keys = new int[2];
  

  static String decryptKeys(char[] keysChar){
    for (int m=0; m<2; m++){
      for (int i=0, n=alphabet.length(); i<n; ++i){
        if (keysChar[m]==alphabet.charAt(i))
          keys[m] = i;
      }
    }
    return text.substring(2);
  }


  //Method that will shift the encrypted alphabet back
  //with keys what you entered in main method.
  static String[] shiftAlphabetDecrypt (int[] keys){ 
      String[] alphabetShifted = {alphabet.substring(alphabet.length()-keys[0])+
                                  alphabet.substring(0, alphabet.length()-keys[0]),
                                  alphabet.substring(alphabet.length()-keys[1])+
                                  alphabet.substring(0, alphabet.length()-keys[1])};
      return alphabetShifted;
  }
  
  //Main method.
  public static void main (String[] args){
    scan.reset();
    System.out.println("\n\n\nPlease enter the encrypted text:");
    text = scan.nextLine();
    scan.close();
    
    char[] keysChar = {text.charAt(0), text.charAt(1)};
    System.out.println(ShiftAlphabetEncrypt.encryptAndDecrypt(decryptKeys(keysChar), shiftAlphabetDecrypt(keys), keys));
  }
}

输出：

加密：

Please enter the text that you want to encrypt:
Hello my dear!~

Please enter the key of odd letters
(positive integer):
7

Please enter the key of even letters
(positive integer):
14
hoOsszv af rloy!~

解密：

Please enter the encrypted text:
hoOsszv af rloy!~
Hello my dear!~

实现了输入需要keys，输出不需要。。代码还需优化omg….

第五版

加密：

//Import Scanner.
import java.util.Scanner;
import java.util.Random;

public class Encrypt {
  public final static Random rand = new Random();
  public final static Scanner scan = new Scanner(System.in);
  public final static String alphabet = "abcdefghijklmnopqrstuvwxyz";

  //Encrypte keys to the start of the encrypted code.
  static String encryptKeys(int[] key){
    String keysLetters = "";
    for (int i=0; i<3; ++i)
      keysLetters += alphabet.charAt(key[i]);
    return keysLetters;
  }

  // Method that will shift the alphabet with keys what you entered in main method.
  static String[] shiftAlphabetEncrypt(int[] keys) {
    String[] alphaShifted = { 
      alphabet.substring(keys[0]) + alphabet.substring(0, keys[0]),
      alphabet.substring(keys[1]) + alphabet.substring(0, keys[1])};

    return alphaShifted;
  }

  // Method that encrypt/decrypt the text that you entered with keys in main method.
  public static String encryptAndDecrypt (String text, String[] alphaShifted, int[] keys) {
    StringBuilder textSB = new StringBuilder("");
    int count = 0;
    boolean oddEven = true;
    char textCA;

    for (int i = 0, a = text.length(); i < a; ++i) {
      textCA = text.charAt(i);

      // If character not letter, nothing change.
      if (!(Character.isLetter(textCA))) {
        textSB.append(textCA);
        continue;
      }

      ++count;
      // See is this letter in odd or even position (count only letters).
      if (count % 2 == 1)
        oddEven = true;
      else
        oddEven = false;

      // If this character is not "not letter" (is letter).
      for (int b = 0, c = alphabet.length(); b < c; ++b) {
        

        // Find the original position of this letter.
        if ((Character.toLowerCase(textCA)) == alphabet.charAt(b))

          // Change this letter to the number in same position of new alphabet.
          textSB.append(Character.isUpperCase(textCA) ?   //Ask is this letter in upper case?
                       (Character.toUpperCase(alphaShifted[oddEven ? 0 : 1].charAt(b))) : //Append an upper case letter.
                       (alphaShifted[oddEven ? 0 : 1].charAt(b)));  //Append a lower case letter (no change).
      }
    }

    // Return encrypted/decrypted text back.
    return textSB.toString();
  }

  // Main method.
  public static void main (String[] args){
    //Get text.
    scan.reset();
    System.out.println("\n\n\nPlease enter the text that you want to encrypt:");
    String text = scan.nextLine();
    scan.close();
    
    //Get random keys.
    int[] keys = new int[3];
    for(int i=0; i<3; ++i) 
      keys[i] = rand.nextInt(alphabet.length());
      
    //Output encrypted code.
    System.out.println(encryptKeys(keys)+encryptAndDecrypt(text, shiftAlphabetEncrypt(keys), keys));
  }
}

解密：

//Import Scanner.
import java.util.Scanner;
import Encrypt;

public class Decrypt{
  private static String text;
  private static int[] keys = new int[2];
  
 //Decrypte keys from the start of the encrypted code.
  static String decryptKeys(char[] keysChar){
    for (int m=0; m<2; m++){
      for (int i=0, n=alphabet.length(); i<n; ++i){
        if (keysChar[m]==alphabet.charAt(i))
          keys[m] = i;
      }
    }
    return text.substring(2);
  }


  //Method that will shift the encrypted alphabet back
  //with keys what you entered in main method.
  static String[] shiftAlphabetDecrypt (int[] keys){ 
      String[] alphabetShifted = {alphabet.substring(alphabet.length()-keys[0])+
                                  alphabet.substring(0, alphabet.length()-keys[0]),
                                  alphabet.substring(alphabet.length()-keys[1])+
                                  alphabet.substring(0, alphabet.length()-keys[1])};
      return alphabetShifted;
  }
  
  //Main method.
  public static void main (String[] args){
    scan.reset();
    System.out.println("\n\n\nPlease enter the encrypted text:");
    text = scan.nextLine();
    scan.close();
    
    char[] keysChar = {text.charAt(0), text.charAt(1)};
    System.out.println(Encrypt.encryptAndDecrypt(decryptKeys(keysChar), shiftAlphabetDecrypt(keys), keys));
  }
}

输出：

加密：

第一次运行

Please enter the text that you want to encrypt:
Alittlebear awa QAQ hah!!!
xtlXefmqebubto ttt NTN axa!!!

第二次运行

Please enter the text that you want to encrypt:
Alittlebear awa QAQ hah!!!
ekpEvmdxvilikv kak UKU rer!!!

第三次运行

Please enter the text that you want to encrypt:
Alittlebear awa QAQ hah!!!
zfhZqhysqdgdfq fvf PFP mzm!!!

解密：

第一个解密：

Please enter the encrypted text:
xtlXefmqebubto ttt NTN axa!!!
Alittlebear awa QAQ hah!!!

第二个解密：

Please enter the encrypted text:
ekpEvmdxvilikv kak UKU rer!!!
Alittlebear awa QAQ hah!!!

第三个解密：

Please enter the encrypted text:
zfhZqhysqdgdfq fvf PFP mzm!!!
Alittlebear awa QAQ hah!!!

输入和输出都不需要key了，直接输入需要加密/解密的文字就行。。。目前的做法是把key简单加密放在加密代码前面（放三个key，只用前俩(T_T)）。。慢慢优化吧。。