Why is List list = new ArrayList, not directly with ArrayList

The list is an interface, and ArrayList is a class. ArrayList inherits and implements the list.

ArrayList (); This sentence creates a ArrayList object and then traces it back to the list. At this point it is a list object, some ArrayList have but

ArrayList (); Creating an object preserves all properties of ArrayList.


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LinkedList or vectors and so on, now you're using ArrayList, and maybe someday you need to switch to another implementation class? , you just have to change the line.

Alist = new ArrayList (), which you have changed, especially if you have used ArrayList unique methods and properties.  
, if there is no special need, it is best to use list List = new LinkedList (); , which facilitates the refactoring of program code. This is the benefit of interface-oriented programming

Why is List list = new ArrayList, not directly with ArrayList