Revision comments of the first edition

[gregPerlinLi]

• When implementing interface methods, please add @Override at the beginning and please use loverCamelCase style for method name

  https://github.com/milkcandy23333/Caesar_v2/blob/f15bb7856d7b83ee47c2638699d12744143ba102/src/com/milkcandy23333/CaesarEncryptioImpl.java#L4 Change as:

  @Override
  public String encrypt(String st, int p) {

• The interface does not need to add an abstract signature, because an interface is a pure abstract interface that is more abstract than an abstract class

  https://github.com/milkcandy23333/Caesar_v2/blob/f15bb7856d7b83ee47c2638699d12744143ba102/src/com/milkcandy23333/CaesarEncryption.java#L3 Change as:

  public interface CaesarEncryption {

• Braces must be used in if / else / for / while / do statements, even if there is only one line of code

  https://github.com/milkcandy23333/Caesar_v2/blob/f15bb7856d7b83ee47c2638699d12744143ba102/src/com/milkcandy23333/CaesarEncryptioImpl.java#L43-L45 Change as:

  if (st.charAt(i) - (p % 10) < '0') {
     tmp += 10;
     tmp -= (p % 10);
  }

• It is recommended to use StringBuilder type instead of String type when splicing strings to improve efficiency

  https://github.com/milkcandy23333/Caesar_v2/blob/f15bb7856d7b83ee47c2638699d12744143ba102/src/com/milkcandy23333/CaesarEncryptioImpl.java#L5 Change as:

  StringBuilder ret = new StringBuilder(1024);

• Static variables or static methods of a class should not be accessed through the object reference of a class. There is no need to increase the parsing cost of the compiler. You can access them directly with the class name

  https://github.com/milkcandy23333/Caesar_v2/blob/f15bb7856d7b83ee47c2638699d12744143ba102/src/com/milkcandy23333/Main.java#L48-L49 Change as:

  
  s = Md5Encryption.backMD5(s);

• The while statement cannot be completed without throwing an exception

  https://github.com/milkcandy23333/Caesar_v2/blob/f15bb7856d7b83ee47c2638699d12744143ba102/src/com/milkcandy23333/Main.java#L8-L59 Change as:

         while (true) {
             System.out.println("This is a Caesar encryption/decryption program");
             System.out.println("Press 1 to Encrypt or 2 to Decrypt");
             System.out.println("Press 3 to calculate a string's MD5");
             System.out.println("You can't Decrypt MD5,but you can press 4.");
             int Operator;
             String s;
             int p;
             Operator = scanner.nextInt();
  
             if (Operator == 1) {
                 System.out.println("Step 1:Enter the string to encrypt.");
                 s = scanner.nextLine();
                 s = scanner.nextLine();
                 System.out.println("Step 2:Enter the offset.");
                 p = scanner.nextInt();
  
                 CaesarEncryption X = new CaesarEncryptioImpl();
                 s = X.Encrypt(s, p);
  
                 System.out.println(s);
             }
             if (Operator == 2) {
                 System.out.println("Step 1:Enter the string to decrypt.");
                 s = scanner.nextLine();
                 s = scanner.nextLine();
                 System.out.println("Step 2:Enter the offset.");
                 p = scanner.nextInt();
  
                 CaesarEncryption X = new CaesarEncryptioImpl();
                 s = X.Decrypt(s, p);
  
                 System.out.println(s);
             }
             if (Operator == 3) {
                 System.out.println("Enter the string to calculate MD5.");
                 System.out.println("The length of the result is 32.");
                 s = scanner.nextLine();
                 s = scanner.nextLine();
  
                 Md5Encryption X = new Md5Encryption();
                 s = X.backMD5(s);
  
                 System.out.println(s);
             }
             if (Operator == 4) {
                 Exception e = new UnsupportedOperationException();
                 e.printStackTrace();
                 System.out.println("UnsupportedOperationException");
                 System.out.println("异常信息： MD5 算法无法解密");
             }
             if (Operator > 4 || Operator < 1) {
                 break;
             }
         }

• Do not submit .idea, target compie output directories and .iml file by using .gitignore file

  /target/
  /.idea/
  Caesar_v2.iml

[gregPerlinLi]

Generally speaking, it's very good, except for some details. And you can continue to try to realize the advanced requirements. Please chat with me privately after the modification is completed.

[milkcandy23333]

• [x] Override
• [x] loverCamelCase
• [x] delete abstract before interface
• [x] brace even if there is only 1 command in IF
• [x] StringBuilder
• [x] static methods, directly use their methods instead of using new
• [x] type other integers to quit the program
• [ ] ignore submitting some irrelevant files :sob: :sob: :sob: I don't know how to ignore submitting them!