Question

我一直在自学Java，而且我对循环问题感到困惑。我知道你可以利用'while'循环来帮助将Java程序带回到代码的特定部分......但我不确定如何实现。

以下是我特别关注的内容：在完成代码的有效或无效结果后，我希望它返回到代码中提示用户输入密码的部分。

以下是我的代码的副本......非常感谢任何帮助！

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

对于类似的东西，通常用while

测试布尔值

  boolean check = false;

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

但是，您必须移动用户输入密码的语句才能执行此操作。

  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

您可以使用do-while循环，如下所示。

do{

  // logic to validate

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

这将执行逻辑一次，然后检查中断条件。如果它是true那么它将再次执行逻辑。这一直持续到遇到中断状态或程序终止。

使用Java循环返回到程序的另一部分？

2 个答案: