使用Java循環返回程序的另一個部分？

Question

我一直在自學Java，並且在循環方面受困。 我知道您可以利用“ while”循環來幫助將Java程序帶回到代碼的特定部分……但是我不確定如何實現。

這是我要尋找的：在代碼的有效或無效結果完成后，我希望它返回到提示用戶輸入密碼的代碼部分。

這是下面我的代碼的副本...任何幫助將不勝感激！

import java.util.Scanner;

public class Password {
   public static void main(String[] args) {
      Scanner input = new Scanner(System.in);  

      //Prompts the user to enter a password, and stores password in the string "passwordIn."
      System.out.print("Please enter a password to determine if it is valid or not: ");
      String passwordIn = input.nextLine();

      //Established various boolean checks to be passed in order for code to evaluate each character.
      boolean lengthCheck = false;
      boolean upperCheck = false;
      boolean lowerCheck = false;
      boolean digitCheck = false;
      boolean specialCheck = false;
      boolean check = false;

      //The loop will initiate the testing of the string.   
      for(int i = 0; i < passwordIn.length(); i++) {

      //Character pw represents the index!   
      char pw = passwordIn.charAt(i); 

      //This verifies that the password meets the length (at least 8 characters) requirement.
      if (passwordIn.length() >= 8) {
          lengthCheck = true;
          }   

     //This verifies that there is at least one uppercase letter in the password.
      if(Character.isUpperCase(pw)) {
           upperCheck = true;
           }
     //This verifies that there is at least one lowercase letter in the password.
      if(Character.isLowerCase(pw)) {
           lowerCheck = true;
           }
     //This verifies that there is at least one digit in the password. 
      if(Character.isDigit(pw)) {
           digitCheck = true;
           }

     //This verifies that there is at least one character that is not a letter or a number within the password.  
      if(!Character.isLetter(pw) && !Character.isDigit(pw)) {
           specialCheck = true;
           }
     }

      //Verifies the results of the loop to ensure that all checks are true.
      if(upperCheck == true && lowerCheck == true && digitCheck == true && lengthCheck == true && specialCheck == true) {
           check = true;
           }

      // Uses boolean to determine if password is valid.
      if (check == true) {
       System.out.print("\nThe password you entered was: " + passwordIn);
       System.out.print("\nVerdict: " + "\t" + "Valid");
       }
      else {
       System.out.print("\nThe password you entered was: " + passwordIn);
       System.out.print("\nVerdict: " + "\t" + "Invalid");

      }

   }
}

Answer 1

對於這樣的事情，通常需要一段while測試布爾值

  boolean check = false;

  //The loop will initiate the testing of the string.   
  while(!check) {

但是，您將必須移動從用戶讀取密碼的語句，以執行任何有用的操作。

  boolean check = false;

  //The loop will initiate the testing of the string.   
  while(!check) {

     //Prompts the user to enter a password, and stores password in the string "passwordIn."
     System.out.print("Please enter a password to determine if it is valid or not: ");
     String passwordIn = input.nextLine();

     // ... testing...
  }

Answer 2

您可以如下使用do-while循環。

do{

  // logic to validate

} while(condition); // Your break condition here

這將執行一次邏輯，然后檢查中斷條件。 如果為true則它將再次執行邏輯。 這一直持續到遇到中斷條件或程序終止為止。