Java将字符串和字符串[]传递到另一个类

Question

I am sure this question is answered, I get all kinds of results when I search on it, but I just cant grasp this concept. This is a homework assignment and I prefer to understand which is why I am posting. The assignment is to read user credentials from a file, hash the password, and then if they match display contents of another file that associates with their role.

I wrote this in a single class and then discovered that the assignment calls for at least two classes. So it made sense to me to read the files in 1 class and do everything else in another. It worked very well as one class, but this is my first programming adventure and im only 6 classes in. I do not understand the basics as I should, so in your response if you can teach me why the code needs modified as it does I would be grateful. My code is as follows;

package it145_final;
import java.util.Scanner;
import java.io.IOException;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;

public class IT145_Final {

public static void main(String[] args) throws IOException, NoSuchAlgorithmException {
    Scanner scnr = new Scanner(System.in);
    Scanner fileIn = null;
    int failedAttempts = 0;
    int i = 0;
    String q = "q";
    // objects that I think I need???? Maybe??? but dont know how to get them from the FinalFiles class
    FinalFiles fileAdmin = new FinalFiles();
    FinalFiles fileVet = new FinalFiles();
    FinalFiles fileZoo = new FinalFiles();
    FinalFiles userA = new FinalFiles();
    fileAdmin.file();
    userA.file();

    while (failedAttempts < 3)
        {                
            System.out.println("Enter user name, or q to exit"); //get username
            String userName = scnr.next();     
            if (userName.equalsIgnoreCase(q)) //option to terminiate
                    {
                    System.out.println("Logging Out");
                    break;
                    }   
            System.out.println("Enter password"); // get password
            scnr.nextLine();
            String userPassword = scnr.nextLine();  
                            //The following takes the entered password and hashes it
                            String hashedPass = userPassword;  
                            MessageDigest md = MessageDigest.getInstance("MD5");
                            md.update(hashedPass.getBytes());
                            byte[] digest = md.digest();
                            StringBuffer sb = new StringBuffer();
                            for (byte b : digest) {
                            sb.append(String.format("%02x", b & 0xff));
                                    }


                if (userName.equals(userA[i]) && sb.toString().equals(userA[i + 1]))
                {
                    if (userA[i + 3].equals("admin"))
                    {
                        System.out.println(admin);
                        break;
                    }                        
                    else if (userA[i + 3].equals("veterinarian"))
                    {
                        System.out.println(veterinarian);
                        break;

                    }
                    else if (userA[i + 3].equals("zookeeper"))
                    {
                        System.out.println(zookeeper);
                        break;

                    }
                    else
                    {
                        System.out.println("Failed attempt");
                        failedAttempts ++;
                    }

                }
                if (userName.equals(userB[i]) && sb.toString().equals(userB[i + 1]))
                {
                    if (userB[i + 3].equals("admin"))
                    {
                        System.out.println(admin);
                        break;

                    }                        
                    else if (userB[i + 3].equals("veterinarian"))
                    {
                        System.out.println(veterinarian);
                        break;
                    }
                    else if (userB[i + 3].equals("zookeeper"))
                    {
                        System.out.println(zookeeper);
                        break;
                    }
                    else
                    {
                        System.out.println("Failed attempt");
                        failedAttempts ++;
                    }

                }
                if (userName.equals(userC[i]) && sb.toString().equals(userC[i + 1]))
                {
                    if (userC[i + 3].equals("admin"))
                    {
                        System.out.println(admin);
                        break;
                    }                        
                    else if (userC[i + 3].equals("veterinarian"))
                    {
                        System.out.println(veterinarian);
                        break;
                    }
                    else if (userC[i + 3].equals("zookeeper"))
                    {
                        System.out.println(zookeeper);
                        break;
                    }
                    else
                    {
                        System.out.println("Failed attempt");
                        failedAttempts ++;
                    }

                }
                if (userName.equals(userD[i]) && sb.toString().equals(userD[i + 1]))
                {
                    if (userD[i + 3].equals("admin"))
                    {
                        System.out.println(admin);
                        break;
                    }                        
                    else if (userD[i + 3].equals("veterinarian"))
                    {
                        System.out.println(veterinarian);
                        break;
                    }
                    else if (userD[i + 3].equals("zookeeper"))
                    {
                        System.out.println(zookeeper);
                        break;
                    }
                    else
                    {
                        System.out.println("Failed attempt");
                        failedAttempts ++;
                    }

                }
                if (userName.equals(userE[i]) && sb.toString().equals(userE[i + 1]))
                {
                    if (userE[i + 3].equals("admin"))
                    {
                        System.out.println(admin);
                        break;
                    }                        
                    else if (userE[i + 3].equals("veterinarian"))
                    {
                        System.out.println(veterinarian);
                        break;
                    }
                    else if (userE[i + 3].equals("zookeeper"))
                    {
                        System.out.println(zookeeper);
                        break;
                    }
                    else
                    {
                        System.out.println("Failed attempt");
                        failedAttempts ++;
                    }

                }
                if (userName.equals(userF[i]) && sb.toString().equals(userF[i + 1]))
                {
                    if (userF[i + 3].equals("admin"))
                    {
                        System.out.println(admin);
                        break;
                    }                        
                    else if (userF[i + 3].equals("veterinarian"))
                    {
                        System.out.println(veterinarian);
                        break;
                    }
                    else if (userF[i + 3].equals("zookeeper"))
                    {
                        System.out.println(zookeeper);
                        break;
                    }
                    else
                    {
                        System.out.println("Failed attempt");
                        failedAttempts ++;
                    }

                }


        System.out.println("Login Failed");
        failedAttempts++;
        }







    }




}

You can see I started to create some objects but I just cannot figure out how, or if thats even a good way, to get info from my other class. And the class I created to read the files is;

package it145_final;
import java.io.File;
import java.io.IOException;
import java.util.Scanner;


public class FinalFiles {
     public static void file() throws IOException{


    String admin = "";
    String veterinarian = "";
    String zookeeper = "";
    String[] userA = new String[4];
    String[] userB = new String[4];
    String[] userC = new String[4];
    String[] userD = new String[4];
    String[] userE = new String[4];
    String[] userF = new String[4]; 

        File file0 = new File("C:usercredentials.txt"); // Opens files
            Scanner contents0 = new Scanner(file0);
        File file1 = new File("C:admin.txt"); 
            Scanner contents1 = new Scanner(file1);
        File file2 = new File("C:veterinarian.txt"); 
            Scanner contents2 = new Scanner(file2);
        File file3 = new File("C:zookeeper.txt"); 
            Scanner contents3 = new Scanner(file3);

            // Following reads the files and assignes to variables as needed
            while (contents1.hasNext())
                {     
                    admin += contents1.nextLine();   
                }
           // System.out.println(admin); used to verify that admin was correct
            while (contents2.hasNext())
                {        
                    veterinarian += contents2.nextLine();   
                }
            while (contents3.hasNext())
                {    
                    zookeeper += contents3.nextLine();   
                }              
            while(contents0.hasNext())
                {                
                    String user1 = contents0.nextLine();//grabs the line from the file for each individual user
                    String user2 = contents0.nextLine();
                    String user3 = contents0.nextLine();
                    String user4 = contents0.nextLine();
                    String user5 = contents0.nextLine();
                    String user6 = contents0.nextLine();
                    userA = user1.split("\t");//takes information on user and breaks it into an array                       
                    userB = user2.split("\t");
                    userC = user3.split("\t");
                    userD = user4.split("\t");
                    userE = user5.split("\t");
                    userF = user6.split("\t");

                System.out.println(userB[0]);  //using for testing to make sure I am getting the correct info
                System.out.println(userB[1]);

                }

     }

}

I know its not neat and tidy and I am sure there are better ways for me write something like this, I just did what I though of and what I know. I think if somebody could just show me how to pass those strings(admin, veterinarian, and zookeeper) along with the String[], userA userB etc. into my main it would work again and be sufficient for somebody with my skill level.

Cheers Andy

Answer 1

As you are at entry level coding i would try to help you understand the logic a little which is essential to making a good application.

To make it easier for yourself you should think that each task needs a class. In your case you should have one class for obtaining the files and another for checking password. keep in mind that there is always one dominant class that launches the application and contains the main method.

In these individual classes you should create methods to break down the processes making the code more clear. In the password checking class you would want a method for each of these jobs (reading the files, encrypting password, decrypting password, checking the credentials against eachother).

Then return the value back to the first class. So it would look something like this.

class Main { //first class
    public static void main(String[] args){
        File = new File("file1"); //obtain file 1
        File = new File("file2"); //obtain file 2
        PasswordCheck checker = new PasswordCheck(); // call instance of second class

        boolean credentialOk= passwordCheck.process(file1,file2)//calls method in second class and returns if the credentials match
    }
}

class PasswordCheck { //second class
   public passwordCheck(){

   }//inistialise class

   public boolean process(File file1, File file2){

   }// method to process the files and returns if match succesfully or not 
}