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methods (size(), get(), indexOf(). toArray()) of a list is observers?

 
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Just a simple question is this methods of an arraylist is called an observer methods ?
 
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I've never heard of "observer methods". We call methods like that "accessors". Methods that modify an object (in the case of a List, a method like add()) are called "mutators".
 
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You can try reading about observers in this old thread. When I first saw the question, that is what I thought you meant.

I have copied Christophe Verré's code with additional indentation, otherwise unchanged:-It is conventional to write public before static but not compulsory.
 
Abdullah Attia
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Very Grateful for help, Thank you Stephan van Hulst
Thank you Campbell Ritchie your answer maybe what i'm looking for

But
in this link : http://web.mit.edu/6.005/www/fa14/classes/08-abstract-data-types/

he says

Observers take objects of the abstract type and return objects of a different type. The size method of List, for example, returns an int.



also he says while talking about lists

observers: size, get



and the exercise i'm solving asking me to develop a data type with minimum 3 mutators and minimum 3 observers
So i think it means what i have found in the link above
i just want to make sure
 
Stephan van Hulst
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To me it seems silly to make a distinction between "producers" and "observers". Like I said, we just call them "accessors". But yes, it seems your understanding is correct.

After your classes, I would recommend forgetting those meanings of the words, because in Java, "producers", "observers", etc... are usually used for certain design patterns.
 
Campbell Ritchie
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I would not say that is a standard use for the word observer.
 
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