Java将信息传递给构造函数

Question

I have a working program here, it takes user input (a password) and checks conditions (is it 8 chars, contains one uppercase, one lowercase, and a digit) then writes the information to a file.

It compiles and runs, but upon further review of the instructions for the assignment, I must use an object to call the methods. This is throwing me off. I think I would use a statement like: password.PasswordCheck(pwd); but I am not sure how this would work with what I have or where to put.

Currently my method toString is in charge of building the string to display the info to the user and does it by calling the method acceptable.

What must I do to change this so that everything is using the object to call?

Thanks so much!

import java.util.Scanner;   
import java.io.*;           

public class PasswordCheck //create the class
{
       private boolean isEightCharacters;  //true if has 6 characters, false if                                                                                  doesn't
       private boolean hasOneUppercase;  //true if has 1 uppercase character, false if doesn't
       private boolean hasOneLowercase;  //true if has 1 lowercase character, false if doesn't
       private boolean hasOneDigit;      //true if has 1 digit, false if doesn't
       public boolean isPasswordValid;  //true if all other conditions are true, false otherwise
       private String password;         //global variable declaring string

       //create default constructor
       public PasswordCheck(){

          isEightCharacters = false;    //default value
          hasOneUppercase = false;      //default value
          hasOneLowercase = false;      //default value
          hasOneDigit = false;          //default value
          isPasswordValid = false;      //default value

       }

       //create constructor with string as input
       public PasswordCheck(String pwd){
          password = pwd;   //set password to the variable being passed in
          setEightCharacters();   //call the method
          setOneUppercase();      //call the method
          setOneLowercase();      //call the method
          setOneDigit();          //call the method
          setPasswordValid();     //call the method            

       }

       //create methods to change attributes/fields above
       public void setEightCharacters(){

           if (password.length() >= 8)  //if statement to validate password length
          {
             isEightCharacters = true;  //if passes condition test, set to true
          }   
          else  //if not 8 characters
          {
             isEightCharacters = false;    //set boolean to false
          }
       } 

       public void setOneUppercase(){   //method to check if password contains uppercase letter

         int i;    //declare count variable
         char ch;  //declare char variable
         boolean hasUpper = false;   //declare and initialize boolean to false

         for ( i = 0; i < password.length(); i++ ) {   //begin loop to read through string

             ch = password.charAt(i);   //sets ch to character in position of string
             if (Character.isUpperCase(ch))   //tests to see if character is uppercase
             {    
                 hasUpper = true;    //sets boolean to true
             }

         }

             if(hasUpper == true)    
             {
                hasOneUppercase = true;
             } 
             else 
             {
                hasOneUppercase = false;
             }
       }

       public void setOneLowercase(){   //method to check if password contains lowercase letter

         int i;    //declare count variable
         char ch;  //declare char variable
         boolean hasLower = false;   //declare and initialize boolean

         for ( i = 0; i < password.length(); i++ ) {   //begin loop

             ch = password.charAt(i);
             if (Character.isLowerCase(ch))   //tests to see if string contains lowercase letter
             {    
                 hasLower = true;
             }

         }

             if(hasLower == true)
             {
                hasOneLowercase = true;
             } 
             else 
             {
                hasOneLowercase = false;
             }
       }

       public void setOneDigit(){    //method to see if string contains a number

         int i;    //declares the count variable
         char ch;  //declares the char variable
         boolean hasNumber = false;     //declares and intializes the boolean variable

         for ( i = 0; i < password.length(); i++ ) {   //begin loop

             ch = password.charAt(i);
             if (Character.isDigit(ch)) //tests to see if character is a number
             {    
                 hasNumber = true;
             }

         }

             if(hasNumber == true)
             {
                hasOneDigit = true;
             } 
             else 
             {
                hasOneDigit = false;
             }
       }

       public void setPasswordValid(){     //method to test is all conditions are met for a valid password

          if (isEightCharacters && hasOneUppercase && hasOneLowercase && hasOneDigit == true) //if all true
          {
             isPasswordValid = true;
          }
          else
          {
             isPasswordValid = false;
          }
       }



       //create a method to check ok or missing, pass in one of the booleans
       public String acceptable(boolean x) {

          String var="";
            if (x == true)
             var = "OK";
            else
             var = "Missing";

          return var;    //return statement
       }

       //create a method to validate all conditions
       public String validate(boolean x) {

          String valid="";
             if (x == true)
                valid = "\nPassword is valid.";
             else
                valid = "\nPassword is not valid.";

          return valid;     //return statement
       }

       // toString creates a string with the output
       public String toString(){
          String stringToReturn="";  //declare the string to return

          stringToReturn += validate(isPasswordValid)+
          "\n\n8 characters:  "+ acceptable(isEightCharacters)+ "\n\n1 uppercase:  "+ acceptable(hasOneUppercase)
          +"\n\n1 lowercase:  "+acceptable(hasOneLowercase)+"\n\n1 digit:  "+acceptable(hasOneDigit);

          return stringToReturn;
       }


       public static void main(String[] args) throws IOException
        {
          //variables
          String filename = "passwordCheck.txt";
          String pwd;

          //Welcome message
          System.out.println("Welcome to the Password Check Program!\n");

          //Create scanner object for keyboard input
          Scanner keyboard = new Scanner(System.in);

          //prompt user for the password
          System.out.println("Please enter the password to verify: ");
          pwd = keyboard.nextLine(); //stores the input

          //create object using String as password
          PasswordCheck password=new PasswordCheck(pwd);  //remember to change PasswordCheck based upon new name of class/filename

          //display the validated information
          System.out.println(password);  //uses toString() method for display

          //make sure file does not exist
          File file = new File(filename);
          if (file.exists())
          {
             System.out.println("\nFile " + filename + " already exists. Output not written.");

             System.exit(0);
          }

          //Open the file
          PrintWriter outputFile = new PrintWriter(file);

          //Write the password to the file
          outputFile.println(password);

          //Close the file
          outputFile.close();
          System.out.println("\nOutput written to " + filename);

        }
    }

Answer 1

From my understanding of your question, I think you need to use object's reference variable to call the methods in it. So instead of calling all your methods inside the constructor, call them in your main method as shown below.

More info: By not calling all methods inside a constructor, you have the freedom of calling only those methods that you want to, in your main method. For example in any application you want your password to be at least 8 characters long and not necessarily have a digit, lowercase/uppercase alphabet then you can just call one required method.

Let the constructor be like this

public PasswordCheck(String pwd){
          password = pwd;   //set password to the variable being passed in         
       }

Then in your main method

PasswordCheck password=new PasswordCheck(pwd);
password.setEightCharacters();   //call the method
password.setOneUppercase();      //call the method
password.setOneLowercase();      //call the method
password.setOneDigit();          //call the method
password.setPasswordValid();

Answer 2

My interpretation is that you need to have all your password verification methods as instance methods of PasswordCheck.

So something like

  public PasswordCheck(){
      private String password;

      public PasswordCheck(String pwd){        
          password = pwd
      } 

      // Below you have all your verification methods
      public void isEightCharacters(){
         if (password.length() >= 8){
             System.out.println("Valid");
         }   
         else {
             System.out.println("invalid"); 
         }

      }
      // etc.etc.

   }

And in your main method do something like:

PasswordCheck password=new PasswordCheck(pwd);   
// Call all your verification method
password.isEightCharacters();
// etc.etc.

Answer 3

我认为它想让您创建一个对象密码，并在构造函数中使其符合条件，密码很可能只有一个字符串变量可以接收，然后您可以检查该密码是否正确