Getting null expection thrown at me when everything seems to be declared correctly

Question

I'm trying to hide a password for a bank ATM, and i'm getting a null exception for a char[] deceleration. My classmate and professor can't see why I'm getting this thrown at me as everything is correct in the code. The funny thing is it runs fine on repl.it but I get the exception thrown at me on eclipse and netbeans. The int 'pass' is declared earlier in the code and the getPassword() function is declared on another class where it returns an integer password.

I've tried declaring the char[] before assigning it to readPassword() from the console

   //allows you to log in with valid account. not case sensitive
   else if (choice.equals("L") || choice.equals("l"))
   {
     System.out.print("\nPlease enter your id: ");
     id = scnr.nextInt();
     scnr.nextLine();
     Console console = System.console();
     System.out.print("Please enter your password: ");
     char passChar[] = new char[100];
     passChar = console.readPassword();
     String passPars = new String(passChar);
     pass = Integer.parseInt(passPars);

     //verifies id and password
     for (CustomerAccount i : list)
     {
       if (i.getId() == id && i.getPassword() == pass) 
         {
           obj = i;
           check = true;
           break;
          }
     }

Here is the ran code where the expection is thrown at me -- Please enter your id: 123 Exception in thread "main" java.lang.NullPointerException at Main.main(Main.java:76) Please enter your password: 123

I expect it to say "Please enter your password: " and you enter the password on that line and it is hidden text in the console.

It would appear that `console.readPassword()` is returning null. — Robert Harvey, Oct 08 '19 at 18:51
Can you post the full exception including the stack dump lease? It is unclear what line is raising the exception! — Lev M., Oct 08 '19 at 18:52
Can you show your whole class please? And indicate which line the exception occurs on? Otherwise, all we can do is guess. — Dawood ibn Kareem, Oct 08 '19 at 18:52
Please enter your id: 123 Exception in thread "main" java.lang.NullPointerException at Main.main(Main.java:76) Please enter your password: — WeepingWillow, Oct 08 '19 at 18:54
@WeepingWillow please edit the entire stacktrace into your post. Comments have a character limit and lack formatting. — The Head Rush, Oct 08 '19 at 18:55
this check isn't right: `i.getPassword() == pass`. when comparing `String` (or any other object), you should use `.equals()`. — Kaan, Oct 08 '19 at 19:00
@kaan the string is parsed to an int before put into the loop, and this isnt the problem causing the exception. — WeepingWillow, Oct 08 '19 at 19:01
I'm trying to edit the post to include the whole code but stack overflow is hating me — WeepingWillow, Oct 08 '19 at 19:01
Try capturing input some other way, not `Console`. Most likely `System.console()` is returning null. You can check it by running this: `System.out.println("console: " + System.console());` — Kaan, Oct 08 '19 at 19:02
check link https://stackoverflow.com/questions/104254/java-io-console-support-in-eclipse-ide — caot, Oct 08 '19 at 19:07

score 3 · Answer 1 · answered Oct 08 '19 at 18:57

3

System.console() often returns null within the IDE. Take a look at the documentation for it:

Returns the unique Console object associated with the current Java virtual machine, if any.

Returns:The system console, if any, otherwise null.

Try using a Scanner instead:

Scanner in = new Scanner(System.in);
String line = in.nextLine();

answered Oct 08 '19 at 18:57

Malt

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I was originally using a scanner but switched to the console because I'm trying to hide the text so that when the user is entering the password it does not show up on the screen. I'm seeing that my problem is the console is returning null but I'm unsure how to make it so that it doesn't. Do i need to push something to the console so that when the system.console() takes place it doesn't return null? – WeepingWillow Oct 08 '19 at 19:07
@WeepingWillow Take a look a this answer: https://stackoverflow.com/questions/4203646/system-console-returns-null – Malt Oct 08 '19 at 19:19
It’s probably null just in the IDE – Malt Oct 08 '19 at 21:09

Getting null expection thrown at me when everything seems to be declared correctly

1 Answers1