Why do we assign types to objects that are different to an object's reference type in Java?

Question

Java Newbie here

New instances are stored in variables. However, I see sometimes, that the type of the variable is different from the reference type of the object.

Y y = new x

Why do programmers do this?

https://stackoverflow.com/questions/383947/what-does-it-mean-to-program-to-an-interface?r=SearchResults&s=1|373.7118 — GriffeyDog, Aug 05 '20 at 19:08
This Oracle Java tutorial on [Interfaces and Inheritance](https://docs.oracle.com/javase/tutorial/java/IandI/index.html) may help you. — Scratte, Aug 05 '20 at 19:17

score 0 · Accepted Answer · answered Aug 05 '20 at 19:02

Because sometimes you have common interface for different implementations. For example

List<String> exampleList = new ArrayList<>();

and the other one

List<String> exampleList = new LinkedList<>();

Interface List provide for us the same methods for this two implementations, but how this methods works depends on implementation. Welcome

score 0 · Answer 2 · answered Aug 05 '20 at 19:03

0

Most time Y in your example is an interface so you can change later the Implementation without to change the rest of your application

answered Aug 05 '20 at 19:03

Thomas

2 Answers2