Java loop problem

[VUKI656]

*NOTE: i'm just starting out, so if i made some really stupid mistakes, don't bash me with them.

 

 

I am creating a program where you have to insert the right password else it gives you one less try and you can try again. If you fail 3 times it locks. I already made something similar but i had the problem where it also didn't recognize the correct password. After i deleted it and quit, tried again and now i wrote this from scratch and a lot more things don't work as they should. 

 

PROBLEMS

1. How to make the while loop take the input(password in this case) and compare it to the correctPass. I just wrote 1 != 2 so it loops until it executes "else" and then breaks out of the loop, but it doesn't work. 

2. Also the "attempt" subtraction part also doesn't work. 

3. If i enter the correct password it still gives me the "Try again"

 

Heres the code

 

importjava.util.Scanner; public class Application {public static void main(String[] args) { while(1 != 2) { String correctPass = "Java"; System.out.println("Enter the password"); Scanner input = new Scanner(System.in);String line = input.nextLine(); if(line == correctPass) {System.out.println("Wellcome back sir!");break;}else {intnum = 3;System.out.println("Wrong password, please try again! "  + num + " attempts left!");num = num - 1;if(num == 0) {System.out.println("System Locked!");break;}}  }}}

Edited May 14, 2015 by colonel_mortis
Code tags

[Zambonie]

Well.. for problem #2, your reseting the num to 3 every time it loops.

 

Put int num = 3; outside the while loop.

[VUKI656]

Well.. for problem #2, your reseting the num to 3 every time it loops.

 

Put int num = 3; outside the while loop.

I did but still nothing, or did i placed it wrong? 

[VUKI656]

Isnt break; going to stop it if it executes? How exactly should i type the .equals ?

[ObilvionNizer]

-snip-

Try this:

 

import java.util.Scanner; public class Application {public static void main(String[] args) { while(1 != 2) { String correctPass = "Java"; System.out.println("Enter the password");Scanner input = new Scanner(System.in);String line = input.nextLine(); if(line == correctPass) {      System.out.println("Wellcome back sir!");}      else {            intnum = 3;            System.out.println("Wrong password, please try again! "  + num + " attempts left!");            num = num - 1;}      if(num == 0) #            {            System.out.println("System Locked!");            }             break;else {}}}  }}}

 

Edited May 14, 2015 by colonel_mortis
Code tags

[VUKI656]

 

Eh, it will but the 1 != 2 just doesn't seem like the logical way to go about the loop.

 

also, .equals(string), so in your code it will be

if (line.equals(correctPassword))        // do stuff

Thank you so much. That solved to problem when entering the correct password. Now all i need is to figure out the subtraction of the attempts. 

Also for the 1 != 2, what should i put in  instead of that so that it loops until I enter the correct password ?

 

Try this:

 

importjava.util.Scanner;

 

public class Application {

public static void main(String[] args) {

 

while(1 != 2) {

 

String correctPass = "Java";

 

System.out.println("Enter the password");

Scanner input = new Scanner(System.in);

String line = input.nextLine();

 

if(line == correctPass) {

      System.out.println("Wellcome back sir!");

}

      else {

            intnum = 3;

            System.out.println("Wrong password, please try again! "  + num + " attempts left!");

            num = num - 1;

}

      if(num == 0) #

            {

            System.out.println("System Locked!");

            }

             break;

else {

}

}

}

 

 

}

}

}

 

It doesent quite work, it has a lot of errors. What exactly did you do there?

[olbaze]

Thank you so much. That solved to problem when entering the correct password. Now all i need is to figure out the subtraction of the attempts. 

Also for the 1 != 2, what should i put in  instead of that so that it loops until I enter the correct password ?

 

Try the following:

String correctPass = "Java";String line = "";int num = 3;while(!line.equals(correctPass)) {// the rest should go here}

This should fix both of the issues. The subtraction wasn't working because you were initializing the variable num inside the while-loop, which resulted in it being re-initialized back to 3. Generally speaking, you should never initialize variables inside a loop, unless you literally need the variable to be re-initialized for every loop (such as when using random numbers).

 

As for loops that run until a certain condition is fulfilled, the most common way to do it is using while(True) with break and continue statements as necessary. The advantage of using while(True) is that it enables multiple break conditions. However, it can also make the aim of the code hard to follow.

[vorticalbox]

Bare with me as I use c# and i only have small experience in java. I am also writing this on a chromebook any way here is how I would do it's probably not the best coding but it should work.

importjava.util.Scanner; public class Application {public static void main(String[] args) {    //Create attemps    int attempts=0;    //set password    string correctpass="Java";        do    {        System.out.println("Enter the password");             //get user input        Scanner input = new Scanner(System.in);        String line = input.nextLine();            //if password is correct        if (line == correctpass)        {            break;        }else        {            System.out.println("Incorrect");            //increments attemps            attempts++;            //pauses for enter type to try again            //not sure if this work i read its the same as Console.readkey in c#            System.in.read();        }    }while(attempts!=3)    if (attempts < 3)    {        System.out.println("Welcome back sir");    }else    {        System.out.println("system is locked");    }        System.in.read();}

[Mo5]

 

*NOTE: i'm just starting out, so if i made some really stupid mistakes, don't bash me with them.

 

 

I am creating a program where you have to insert the right password else it gives you one less try and you can try again. If you fail 3 times it locks. I already made something similar but i had the problem where it also didn't recognize the correct password. After i deleted it and quit, tried again and now i wrote this from scratch and a lot more things don't work as they should. 

 

PROBLEMS

1. How to make the while loop take the input(password in this case) and compare it to the correctPass. I just wrote 1 != 2 so it loops until it executes "else" and then breaks out of the loop, but it doesn't work. 

2. Also the "attempt" subtraction part also doesn't work. 

3. If i enter the correct password it still gives me the "Try again"

 

Heres the code

 

importjava.util.Scanner; public class Application {public static void main(String[] args) { while(1 != 2) { String correctPass = "Java"; System.out.println("Enter the password"); Scanner input = new Scanner(System.in);String line = input.nextLine(); if(line == correctPass) {System.out.println("Wellcome back sir!");break;}else {intnum = 3;System.out.println("Wrong password, please try again! "  + num + " attempts left!");num = num - 1;if(num == 0) {System.out.println("System Locked!");break;}}  }}}

 

import java.util.Scanner;public class App{    public static void main(String[] args){        //Initialize the password        String correctPass="Java";        //Create an instance of the Scanner (outside loop so you don't waste resources creating it everytime)        Scanner input = new Scanner(System.in);        //attempt counter        int attempts = 0;        while(attempts<3){                //prompt for password                System.out.print("Input password: ");                String line = input.nextLine();                //check if pw is equal to correctPass                if(line.equals(correctPass)){                    System.out.println("Welcome back!");                    break;                    }                else{                    //increment the attempts and notify the user he has (3-#attempts) attempts left                    attempts++;                    System.out.println("Wrong password. You have "+(3-attempts) +" left");                    //if he inputs the pw wrong 3 times it exits the app                    if(attempts==3){System.exit(0);}                    }            }            //Your code starts here :)System.out.println("Body of the app starts here!");    }}

Now it should work

[Guest]

Do not use break or continue. These are basically goto in disguise and make code harder to understand and modify. Use as many flag boolean variables as are needed to keep a loop going and wrap conditional code in if statements as needed. In this case, consider how you might use exceptions to direct control flow; also think about a timeout to prevent bots or ddos.

 

Do not store passwords in plain text and definitely do not hard code them into your source file.