Thread: Scanner and scannobject.close()

Ok, I have this question that involves the Scanner class. Basically, when you want to perform garbage collection and there is a scanner object. You type scannerobject.close(); in your final clause.
My question is...if you make a scanner object in a public class method and then at the end you type object.close(), wHY does this affect the scanner in MAIN???? I haven't tried writing this in a try catch block, but I would think the results would be the same.
Anyways, I'm running a menu in a repitition statement in main. When the method is called, the method asks for user input, does some calculations and returns back to main, except when it gets to
Hey welcome back to my menu(menu displays options to perform various tasks)
type name = objectScanner.nextType(); ERROR
In this case it's a int and nextInt(). int name = object.nextInt();

Well, when I take out the scannerObject.close(); from my public class method, it works. There is something I am not understanding, I have searched the forums and checked many sites on google and I just want to know why I can't put the scanner.close() object in a public class method. <---even though the scanner object in main is different than the one in the public class method.

Exception in thread "main" java.util.NoSuchElementException
at java.util.Scanner.throwFor(Unknown Source)
at java.util.Scanner.next(Unknown Source)
at java.util.Scanner.nextInt(Unknown Source)
at java.util.Scanner.nextInt(Unknown Source)
at Driver.main(Driver.java:13)

I just want to know why I can't put the scanner.close() object in a public class method.
<---even though the scanner object in main is different than the one in the public class method.

Show us with your code that the "even though" is true.

Please post your code correctly.

Originally Posted by GregBrannon

Show us with your code that the "even though" is true.

Please post your code correctly.

LOL???

CLASS DRIVER
MAIN
SCANNER input INITIALIZED
MENU - ENTER CHOICE
REPITITIOUS MENU LOOP{ CHOICE != SENTINEL
OPTION();
OPTION2();

choice = input.nextInt(); error occurs
}

SCANNER CLOSED
END MAIN
END CLASS

CLASS ALIBRARY
INSTANCE VARIABLES
SETGET FUNCTIONS

PUBLIC VOID TAKESOMEVARIABLESANDCALCULATE{
SCANNER scans INITIALIZED

SCANNER.CLOSE(); <--take this out and it works...
}

The code doesn't matter, why scanner is giving me an error does.

--- Update ---

Use your imagination. Why can't I use the Scanner method Close() in a public libary method? Very simple question, I'm not writing code for it.

There is no code to write. It's just a question about scanner method close.

--- Update ---

It's one of those things you either know or you don't.
Like I said, I don't need luck, my programs works but I just want to know why it won't let me use close in a public class method.

Ok ok...give me 5 minutes....

--- Update ---

import java.util.Scanner;
class javaForum{
      static final int SENTINEL = -1;
      public static void main(String[] args){
             Scanner scans = new Scanner(System.in);
                  Forum f = new Forum();
                  system.out.println("Make a choice\n1. firstChoice\n2. secondChoice\n Enter -1 to quit. 
                  int choice = scans.nextInt();
                  while(choice != SENTINEL){
                          if(choice==1){
                                  f.firstChoice();
                          }else if(choice==2){
                                  f.secondChoice();
                          }
                          system.out.println("Make a choice\n1. firstChoice\n2. secondChoice\n Enter -1 to quit. 
                          choice = scans.nextInt(); //error
                   }
             scans.close();
      }
}
 
class Forum{
      public Forum(){
      }
 
      public void secondChoice(){
             Scanner input = new Scanner(System.in);
 
             input.close();
      }
 
      public void firstChoice(){
             Scanner input = new Scanner(System.in);
 
             input.close();
      }
}

--- Update ---

My only conclusion is that you shoulnd't do this. LOL

I have a lot of user input, and I want to divide and conquer. I want to seperate input and use void methods to take in user data and use return methods in the class to do some calculations with this data as their will be hundreds of options available to the user.

--- Update ---

Error message in first post.

Yea sorry I just wrote it and the forum doesn't act like a compiler. I can't install anything on the computer I'm using.

Without Norm's code, just imagining what you posted as "fixed", does what you posted have anything to do with your original question? Where is the code that resembles this remark?

My question is...if you make a scanner object in a public class method and then at the end you type object.close(), wHY does this affect the scanner in MAIN???? . . . <---even though the scanner object in main is different than the one in the public class method.

public static Scanner input = new Scanner(System.in);

then in whatever class you want Driver.input.nextInt(); <--or nextDouble Float Line whatever

Less code, no confusion, 100% of garbage collected in main with close();

--- Update ---

Originally Posted by GregBrannon

Without Norm's code, just imagining what you posted as "fixed", does what you posted have anything to do with your original question? Where is the code that resembles this remark?

I indicated in the pseudocode and code where the error is/was occurring. //Error
In the first post I indicated what error was being received by the client. I realize there are a few different ways of accomplishing this now with less code and less confusion.

Is your latest post a continuation of the question, or is it the answer you've been looking for?

I indicated in the pseudocode and code where the error is/was occurring.

I know you did, and I know that you became frustrated, and this thread was one of the more difficult and frustrating I've read in quite some time, but the reason we couldn't be more helpful, is because there wasn't a clear reason why you'd be getting the error you described with the code you posted. We couldn't tell what was happening without seeing real code that demonstrated the problem.

I'm glad you've arrived at a solution. Be well.

Thanks norm. Lol Greg, have you ever read a word you didn't know the meaning to and it drives you insane until you figure out what it means?
There were so many newbie questions about scanner it was hard to find what I wanted to know by searching google or the forum.
For re-usability purposes I would put the scanner class inside the public class instead of just main. I don't know how much memory is being leaked by leaving it like that without closing it or if the close() method run at the end of main - kinda like norm said is garbage collecting all scanner objects because they all run through the I/o - System.in...... anyways, I'll look into this new issue on my own, thanks again. I look forward to more complex discussions soon.

You do not need to call close on a scanner if you scan the command line. The command line does not need to be closed.
The close method is useful when scanning files or network streams, these need to be closed or otherwise "bad things" might happen. (files not being written to, network partners waiting for input that never comes, etc).
So unless you use System.setIn(...) and change the default input, you do not need to use the close at all in your code.

Just wanted to throw that in.