Object data overlapping.

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May 27th, 2011, 05:25 AM

Anerxomounos

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Homework - Object data overlapping.

I have this code that i'm using to test if my program works, but all the Account type objects are somehow getting the same data inserted.

Code:

Account acc1 = new Account();
       Account acc2 = new Account();
       Account acc3 = new Account();
       acc1.insert("AAA", 1, 2, 3, 4, 5, 6);
       acc2.setCode("CCC");
       acc3.setCode("BBB");

It prints out : BBB 1 2 3 4 5.0 6.0
for all 3 of them, while it should print:
AAA 1 2 3 4 5.0 6.0
CCC 0 0 0 0 0.0 0.0
BBB 0 0 0 0 0.0 0.0

The Account class works perfectly, and I know this because it got 10/10 on my previous project.

May 27th, 2011, 07:50 AM

NormR

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Do you use static variables in the class?

May 27th, 2011, 08:35 AM

Anerxomounos

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Quote:

Originally Posted by NormR

Do you use static variables in the class?

Yes, I do. And please don't tell me that's the problem because I'm gonna murder my java professor!

May 27th, 2011, 08:55 AM

NormR

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With static variables, there is only ONE variable that is shared between all the instances of the class objects. In other words, all the instances of the Account class will have the same value for all variables that are defined as static.

Last edited by NormR : May 27th, 2011 at 09:32 AM.

May 27th, 2011, 08:58 AM

Anerxomounos

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Quote:

Originally Posted by NormR

With static variables, there is only ONE variable that is shared between all the instances of the class objects. In other words, all the instances of the Account class will have the save value for all variables that are defined as static.

Oh my god, I think I have a lot of typing to do...
However, how would I use non-static variables for static methods? (Because my dear prof won't explain anything about static and non-static but still force me to use static in front of my methods. Also my book is crap and provides no guidelines at all regarding this subject.)

For example I need to have this method in my Account class:

Code:

public static String values()
    {
        return code + "\t" + accountNo + "\t" + day + "\t" + month + "\t" + year + "\t" + balance + "\t" + interestRate + "\n";
    }

It needs to be static because it's called by another static method ( a main() in some other class). And it tells me my variables should also be static for it to work. :S

May 27th, 2011, 09:10 AM

NormR

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If the values method is static, it can only see static values.
If you pass a reference to an object as an arg to the values method, then it could get the contents of variables from that object.

Quote:

It needs to be static because it's called by another static method ( a main() in some other class)

You should redesign your code so you don't need to use static.

May 27th, 2011, 09:16 AM

Anerxomounos

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Actually dear friend, don't even bother explaining. It is not your job to teach me, it my professor's.

So I'm getting rid of all the statics and if I don't get a perfect score for that reason, well he can kiss my ***. He can't expect me to know details he hasn't taught me, and I know it might be trivial for many programmers, but I just started java 3months ago and I have read 10 times more information than that included in my pathetic book.

Same thing happened with my other project, where he wanted me to build some calendar without using the Calendar classes. However, he didn't even mention I shouldn't use them, neither did he mention what I should use. Therefor, my project will get some seriously dissapointing grade, despite my countless hours of work on it.

Thanks again for pointing out that static thing, I will surely remember it from now, because I always remember things that infuriate me

May 31st, 2011, 02:40 PM

tfecw

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Colleges are a lot of things, but they are most certainly not about spoon feeding information. No one cares about what your prof did or didn't teach you. You have all the tools and are an adult. Make it happen.

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Homework - Object data overlapping.

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