java - How to create ArrayList properly? -

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this question has answer here:

below 2 ways how create arraylist:

list<string/*or other object*/> arrlist = new arraylist();//imports list, arraylist arraylist<string/*or other object*/> arrlist = new arraylist();//imports arraylist

what difference? method should used?

the first form recommended for public interface of class (say, declaration of attributes in class). it's well-known advice should program interface, not concrete implementation (this stated in design patterns) - number of classes have import has little quality of code , design.

the advantage of first form it'll allow swap implementations later on, if need arises - whereas second implementation sets in stone implementing class, making code harder evolve , less flexible.

there cases when it's ok declare , use concrete classes, though (for instance, little bump in performance). public interface of class should use interfaces whenever possible, it'll make future changes easier implement.


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