如何在Java中使用扫描仪和条件？

Question

I'm fairly new to java and now I'm testing the Scanner ! Here is my code:

package Examples;

import java.util.Scanner;

public class UserLogin
{
    public static void main(String[] args)
    {
        Scanner in= new Scanner (System.in);
        System.out.println("Please enter your name!");
        String keyboard= in.nextLine();    

        System.out.println("Welcome: " + keyboard);
        System.out.println("What is your password?");

        Scanner x= new Scanner (System.in);
        int password= x.nextInt();


        if(password ==14567) 
        {
            System.out.println("Password accepted ! you are welcome!");
        }
        else
        {
            System.out.println("Sorry wrong password! Try again");
            Scanner input = new Scanner(System.in);
            int password2=input.nextInt();
            while (password2==password);
            {
                System.out.println("Welcome!!!!");
            }   
        }
    }   
}        

I want the user's name, password and that is it! But I noticed that when I ask the name even if I press the enter key, it will ask me the password right away. So I want to make sure I get a name. Also when I ask the password I want to be able to give him few chances before saying goodbye.

Please enter your name!
michel
Welcome: michel
What is your password?
12345
Sorry wrong password! Try again
12345

This is what I get on the console.

Thanks!

Answer 1

First things first, You have declared unnecessary scanner objects. You only need to make scanner object once. You can take input using that object as many times as you want.

Second thing is you need to remove semi-colon you have put at the end of while (password2==password); because putting a semi-colon there will execute the block of while loop regardless of whether condition of while loop is true of false.

Now to do what you want, try following code.

public static void main(String[] args) {
 Scanner in= new Scanner (System.in);
 int default_password = 14567;
 int counter = 3;

System.out.println("Please enter your name!");
String keyboard= in.nextLine();    

System.out.println("Welcome: " + keyboard);
System.out.println("What is your password?");

int password= in.nextInt();

if(password == default_password) 
{
    System.out.println("Password accepted ! you are welcome!");

}
else
{
    while(counter > 0)
    {
      System.out.println("Sorry wrong password! Try again");

       password = in.nextInt();

       if (password == default_password)
       {
         System.out.println("Welcome!!!!");
         break;
       }
       else
       {
        counter--;
       }  


    }
    if(counter== 0)
           System.out.println("Good Bye !!");
}

}

Answer 2

You don't need two Scanner since it would work for userName and Pass word. Do-While works fine here. You keep asking for valid pass word. Updated with count 3.

package ab;
import java.util.Scanner;

public class UserLogin{
    public static void main(String[] args) {

        Scanner stdIn= new Scanner (System.in);

        String userName; 
        int userPassWord;

        boolean invaildPassWord = false;

        System.out.println("Please enter your name!");
        userName = stdIn.nextLine();    

        System.out.println("Welcome: " + userName);

        do { 
              System.out.println("\nWhat is your password?");
              userPassWord = stdIn.nextInt();

              if (userPassWord ==14567){
                  System.out.println("Password accepted ! you are welcome!");
                  invaildPassWord = false;
              }

              else {
                  System.out.println("Sorry wrong password! Try again");
                  invaildPassWord = true;

        }

        } while(invaildPassWord);
    }   
}        

Also, you can do it like this. If you don't want "what's your password again and again.

package ab;
import java.util.Scanner;

public class UserLogin{
    public static void main(String[] args) {

        Scanner stdIn= new Scanner (System.in);

        String userName; 
        int userPassWord;

        boolean invaildPassWord = false;

        System.out.println("Please enter your name!");
        userName = stdIn.nextLine();    

        System.out.println("Welcome: " + userName);

        System.out.println("\nWhat is your password?");
        userPassWord = stdIn.nextInt();

        do { 
              if (userPassWord ==14567){
                  System.out.println("Password accepted ! you are welcome!");
                  invaildPassWord = false;
              }

              else {
                  System.out.println("Sorry wrong password! Try again");
                  userPassWord = stdIn.nextInt();
                  invaildPassWord = true;

        }

        } while(invaildPassWord);
    }   
} 

With count 3 times:

package ab;

import java.util.Scanner;

public class UserLogin {
    public static void main(String[] args) {

        Scanner stdIn = new Scanner(System.in);

        String userName;
        int userPassWord;
        int count = 3;

        boolean invaildPassWord = false;

        System.out.println("Please enter your name!");
        userName = stdIn.nextLine();

        System.out.println("Welcome: " + userName);

        System.out.println("\nWhat is your password?");
        userPassWord = stdIn.nextInt();

        if (count > 0) {

            do {
                if (userPassWord == 14567) {
                    System.out.println("Password accepted ! you are welcome!");
                    invaildPassWord = false;
                }

                else {
                    --count;
                    System.out.println("Sorry wrong password! Try again");
                    userPassWord = stdIn.nextInt();
                    invaildPassWord = true;

                }

            } while (invaildPassWord && count > 0);

            System.out.println("GoodBye!");
        }
    }
}

Without goodbye after valid entry:

import java.util.Scanner;

public class UserLogin {
    public static void main(String[] args) {

        Scanner stdIn = new Scanner(System.in);

        String userName;
        int userPassWord;
        int count = 3;

        boolean invaildPassWord = false;

        System.out.println("Please enter your name!");
        userName = stdIn.nextLine();

        System.out.println("Welcome: " + userName);

        System.out.println("\nWhat is your password?");
        userPassWord = stdIn.nextInt();

        if (count > 0) {

            do {
                if (userPassWord == 14567) {
                    System.out.println("Password accepted ! you are welcome!");
                    invaildPassWord = false;
                }

                else {
                    --count;
                    System.out.println("Sorry wrong password! Try again");
                    userPassWord = stdIn.nextInt();
                    invaildPassWord = true;

                }

            } while (invaildPassWord && count > 0);

            if (count <= 0){
                System.out.println("GoodBye!");
            }
        }
    }
}

Answer 3

try this:

while true{
    Scanner x= new Scanner (System.in);
    int password= x.nextInt();
    if(password ==14567)
    {
        System.out.println("Password accepted ! you are welcome")
        break;

    }
    else
    {
        System.out.println("Sorry wrong password! Try again");
}