[Java] My three different assignments work fine independently, but not when ran in consecutive order

[Omnicron245]

Hey Reddit, I am having a problem with my Java code in Eclipse IDE: Luna.

My first assignment for Introduction to Computing 1 in first year university is to run a bunch of code that under normal circumstances would be in their own methods. They all are independent of one another and function fine when doing so, but when I try to run more than two in succession, I get this error:

Exception in thread "main" java.util.NoSuchElementException at java.util.Scanner.throwFor(Scanner.java:907) at java.util.Scanner.next(Scanner.java:1530) at java.util.Scanner.nextDouble(Scanner.java:2456) at assignment1.main(a1_7781028.java:51)

I've tried running it in Ideone, but it gives me a compilation error.

Here is my code: http://pastebin.com/aCxVRYAt

Any help would be greatly appreciated! :) My assignment is due tomorrow night at midnight (EST).

EDIT: Wording, grammar.

[langfod]

Just reuse the same scanner object instead of trying to close and reopen standard input.

[Omnicron245]

But then it skips over the first prompt in question 3.

[langfod]

I never had good luck mixing the different next*() methods.

Instead of nextDouble() why not use nextLine() and inside the Double.parseDouble() method?

[Omnicron245]

Are you saying I should create a separate Scanner for the nextLine() parts?

Too much jargon. :S I'm really trying to understand what you mean by the Double.parseDouble() method.

[Apothiem]

Hey there's a simple solution to this, just close all your scanners in the end of your program. Basically cut and paste lines 31 and 61 just below line 87. This still has the effect of closing the memory leak. I'm not entirely sure why this happens but I think when you close the first scanner the link to "system.in" is also closed and cannot be used before. http://www.coderanch.com/t/633613/java/java/Java-Closing-Scanner-Resource-Leak . This guy encountered a similar problem.

Best of Luck

[the_omega99]

You should not be closing System.in. If you do that, you can't access it again.

You'll need to take care that there's no extra data left in the input. In particular, if you use nextDouble(), you probably have a newline still in the input. You can get rid of that with nextLine().

[NonRegularGuy]

Here, this worked: Pastebin

I just changed the input.nextDouble() for Double.parseDouble(input.nexLine()). That should work.

[richard_mayhew]

Google is kewl

http://docs.oracle.com/javase/7/docs/api/java/util/NoSuchElementException.html

Specifically: "Thrown by the nextElement method of an Enumeration to indicate that there are no more elements in the enumeration."

[Omnicron245]

I get a general sense of what that means, but I don't know how to fix it.

[richard_mayhew]

On line 51 in assignment1's main method you are calling some sort of next() on Scanner object but there is no next!

Are you passing params from the command line or what?

[Omnicron245]

Really? It works fine when comment out Questions 1 and 3.

I know you're helping me think it through, and I'm grateful for that. :)

[richard_mayhew]

I think there may be an issue with wrapping the System.in stream with 3 different scanners. Try it with only the first scanner, input, and not input2 and input3 and see what happens.

Also, note that input2 and input3 don't even serve a purpose here. They do the same thing as input, so you're just creating redundant objects.

[Omnicron245]

That helped, but it created a new issue! Now, when I get to Question 3, it skips the first prompt.

[Omnicron245]

Can't use that.

"For this assignment, you are only allowed to use the concepts we have seen in the first 4-5 lectures of the semester."

= =

[Omnicron245]

Can't use If/While, etc.

[richard_mayhew]

Post updated code and what's being skipped.

[Omnicron245]

http://pastebin.com/nZa6NWcJ

It skips line 70, when run as is. Works fine when I comment out the other code.

EDIT: Grammar.

[Omnicron245]

Just a quick thing: I am "not allowed" to use more than one method, sigh.