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Compile Error Vs runtime Error

Harikrishna Gorrepati
Ranch Hand

Joined: Sep 23, 2010
Posts: 422
Hi,

Why I am getting one error in loop during compile time and similar error during Runtime in the other loop?



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Wouter Oet
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Joined: Oct 25, 2008
Posts: 2700

First of all please QuoteYourSources.

The compile time error is because you're trying to compare a null (reference to nothing) to a primitive boolean. That can't be done. It's like comparing apples to your left shoe. They are completely different.

The NullPointerException is caused by auto-unboxing of the second value of the Boolean array. Note that it is a wrapper Boolean not a primitive thus it's default value is null.


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Please correct my English.
Arjun Srivastava
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Joined: Jun 23, 2010
Posts: 432

Wouter Oet wrote:The compile time error is because you're trying to compare a null (reference to nothing) to a primitive boolean. That can't be done. It's like comparing apples to your left shoe. They are completely different.
The NullPointerException is caused by auto-unboxing of the second value of the Boolean array. Note that it is a wrapper Boolean not a primitive thus it's default value is null.


this time it works fine*
as null is comparable to object,also wrapper classes,is it so?


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Trivikram Kamat
Ranch Hand

Joined: Sep 26, 2010
Posts: 155
Arjun Srivastava wrote:
this time it works fine*
as null is comparable to object,also wrapper classes,is it so?


Yeah, it must be the correct reason.
An Object can be given a null reference. So, it can be compared to a null.
And all classes are derived from Object class in Java (except Object class of course). So, instances of Wrapper classes can be compared to that of Object class.


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It is sorta covered in the JavaRanch Style Guide.
 
subject: Compile Error Vs runtime Error
 
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